US3058997A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Phthalic acid products purification
Assignee: Richfield Oil Corp
•
Filing: 1958-05-23
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Granted: 1962-10-16
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Expires: 1978-05-23
Abstract
No abstract record available.
Inventors
- 👤 Taylor Richard Perry
- 👤 James C Selover
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 17:59
CPC Classifications
C; C07; C07C; C07C51/00; C07C51/42; C07C51/43; C07C51/44
Claims Analysis
Total Claims: 1
Claim 1
Independent Claim
88 words
IN A PROCESS FOR TREATING CRUDE, MOLTEN ORTHOPHTHALIC ANHYDRIDE OBTAINED BY NITRIC ACID OXIDATION OF A METHYLSUBSTITUTED BENZENE TO PRODUCE ORTHOPHTHALIC ACID CONTAINING NITROPHTHALIC ACID IMPURITY, DEHYDRATION OF THE ORTHOPHTHALIC ACID, REDUCTION OF THE NITROPHTHALIC ACID IMPURITY TO AMINOPHTHALIC ACID IMPURITY AND MELTING OF THE ORTHOPHTHALIC ANHYDRIDE, THE STEP WHICH COMPRISES DISTILLING SAID REDUCED, MOLTEN ANHYDRIDE AT A TEMPERATURE GREATER THAN ABOUT 130*C. AND LESS THAN THE DECOMPOSITION TEMPERATURE OF THE ANHYDRIDE TO SEPARATE ANHYDRIDE OVERHEAD FROM HIGHER-BOILING MATERIALS TO OBTAIN SAID ANHYDRIDE SUBSTANTIALLY FREE OF NITRO COMPOUNDS.
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) | 1965-10-15 | 1966-04-16 | 1966-10-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1969-10-15 | 1970-04-16 | 1970-10-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1973-10-15 | 1974-04-16 | 1974-10-16 | $7700.00 | Window Closed / Lapsed |