Patent US3920058A successfully refreshed from Google Patents.
Patent US3769087A successfully refreshed from Google Patents.
US3769087A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ferromagnetic chromium dioxide crystals
Assignee: BASF SE
•
Filing: 1972-04-18
•
Granted: 1973-10-30
•
Expires: 1992-04-18
Abstract
Abstract The invention relates to ferromagnetic chromium dioxide crystals which are particularly suitable as magnetic pigments for magnetic recording media and whose surface, for the purpose of stabilization, is protected with antimony or arsenic compounds which are sparingly soluble in water, and to a process for the production of chromium dioxide crystals thus stabilized by the precipitation of antimony or arsenic compounds which are sparingly soluble in water.
Inventors
- 👤 B Leutner
- 👤 M Schwarzmann
- 👤 M Ohlinger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 17:01
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70636; C; C01; C01G; C01G37/00; C01G37/02; C01P; C01P2004/00; C01P2004/80; C01P2004/82; C01P2004/84; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/31504; Y10T428/31786
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
24 words
A ferromagnetic composition as set forth in claim 1, wherein the antimony or arsenic compound is an oxide or sulfide of antimony or arsenic.
Claim 2
Dependent Claim
54 words
A ferromagnetic composition as set forth in claim 1, wherein the ferromagnetic composition is coated with a mixture of said antimony or arsenic compound and amorphous silicic acid, said silicic acid being present in an amount of 0.5 to 30 percent by weight based on the weight of said chromium dioxide, calculated as SiO2.
Claim 3
Dependent Claim
30 words
A ferromagnetic composition as set forth in claim 3, wherein the amount of amorphous silicic acid is 2 to 6 percent by weight of the chromium dioxide, calculated as SiO2.
Claim 4
Dependent Claim
38 words
A ferromagnetic composition as set forth in claim 1, wherein the coated ferromagnetic composition is additionally coated with amorphous silicic acid in an amount of 0.5 to 30 percent by weight of the ferromagnetic composition, calculated as SiO2.
Claim 5
Dependent Claim
25 words
A magnetic recording medium which comprises: a base and a magnetizable layer, said magnetizable layer containing a ferromagnetic composition as set forth in claim 1.
References Cited (Backward Citations)
US2923683A
Cited
US3520811A
Cited
US3585141A
Cited
US3512930A
Cited
US3586630A
Cited
US3686031A
Cited
US3634252A
Cited
US3687726A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-29 | 1977-04-30 | 1977-10-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-29 | 1981-04-30 | 1981-10-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-29 | 1985-04-30 | 1985-10-30 | $7700.00 | Window Closed / Lapsed |