Patent US2529448A successfully refreshed from Google Patents.
US2529448A
Expired / Lapsed
US
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Purification of phthalic anhydride
Assignee: Monsanto Chemicals Ltd
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Filing: 1949-01-18
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Granted: 1950-11-07
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Expires: 1969-01-18
Abstract
No abstract record available.
Inventors
- 👤 Conover Courtney
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 19:34
CPC Classifications
C; C07; C07C; C07C51/00; C07C51/54; C07C51/573
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
55 words
A METHOD OF PURIFYING CRUDE PHTHALIC ANHYDRIDE WHICH COMPRISES HEATING A MIXTURE OF SAID CRUDE PHTHALIC IN THE PRESENCE OF SULFAMIC ACID AT A TEMPERATURE ESSENTIALLY ABOVE 270*C. FOR A PERIOD OF TIME SUFFICIENT TO PERMIT SEPARATION OF PHTHALIC ANHYDRIDE FROM THE IMPURITIES THEREIN BY DISTILLATION; AND THEN DISTILLING PHTHALIC ANHYDRIDE THEREFROM IN PURIFIED FORM.
Claim 2
Independent Claim
55 words
A METHOD OF PURIFYING CRUDE PHTHALIC ANHYDRIDE WHICH COMPRISES HEATING A MIXTURE OF SAID CRUDE PHTHALIC IN THE PRESENCE OF SULFAMIC ACID AT A TEMPERATURE ESSENTIALLY ABOVE 270*C. FOR A PERIOD OF TIME SUFFICIENT TO PERMIT SEPARATION OF PHTHALIC ANHYDRIDE FROM THE IMPURITIES THEREIN BY DISTILLATION; AND THEN DISTILLING PHTHALIC ANHYDRIDE THEREFROM IN PURIFIED FORM.
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) | 1953-11-06 | 1954-05-08 | 1954-11-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1957-11-06 | 1958-05-08 | 1958-11-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1961-11-06 | 1962-05-08 | 1962-11-07 | $7700.00 | Window Closed / Lapsed |