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Patent US3540987A successfully refreshed from Google Patents.
US3540987A
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US
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Purification of phthalic anhydride by batch distillation,accumulation and continuous distillation
Assignee: GEA Group AG
•
Filing: 1968-05-22
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Granted: 1970-11-17
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Expires: 1988-05-22
Abstract
No abstract record available.
Inventors
- 👤 Otto Garkisch
- 👤 Wolf Mehner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 11:38
CPC Classifications
C; C07; C07C; C07C51/00; C07C51/54; C07C51/573; Y; Y10; Y10S; Y10S203/00; Y10S203/13; Y10S203/20
Claims Analysis
Total Claims: 0
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1973-11-16 | 1974-05-18 | 1974-11-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1977-11-16 | 1978-05-18 | 1978-11-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1981-11-16 | 1982-05-18 | 1982-11-17 | $7700.00 | Window Closed / Lapsed |