US3775434A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for preparing a 3,4,9,10-perylene-tetracarboxylic acid dianhydride pigment
Assignee: Hoechst AG
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Filing: 1971-05-20
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Granted: 1973-11-27
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Expires: 1991-05-20
Abstract
Abstract FINISHING PROCESS FOR IMPROVING THE PIGMENT PROPERTIES OF 3,4,9,10-PERYLENE-TETRACARBOXYLIC ACID DIANHYDRIDE BY PRECIPITATING THE FREE ACID THEREOF FROM AN AQUEOUS ALKALINE SOLUTION OF A SALT OF THE ACID, HEATING THE PRECIPITATED ACID IN AN ORGANIC SOLVENT AT ELEVATED TEMPERATURE TO FORM THE DIANHYDRIDE AND ISOLATING THE DIANHYDRIDE.
Inventors
- 👤 E Spietschka
- 👤 J Landler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 05:38
CPC Classifications
C; C09; C09B; C09B67/00; C09B67/0001; C09B67/0014; C09B3/00; C09B3/14
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) | 1976-11-26 | 1977-05-28 | 1977-11-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-26 | 1981-05-28 | 1981-11-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-26 | 1985-05-28 | 1985-11-27 | $7700.00 | Window Closed / Lapsed |