Method of producing dianhydrides of aromatic tetracarboxylic acids
Abstract
Abstract A method of producing dianhydrides of aromatic tetracarboxylic acids, characterized by the general formula WHERE R stands for A. ARYLENE; B. A GROUP-CH-N-R''''-N CH-, where R'''' is arylene or C. A GROUP WHERE R'''''' is WHERE RIV, H, OH or O is D. IS A GROUP -CH2-OCO-Rv-COOCH2where Rv is arylene E. R is absent; R'' is hydrogen, phenyl, naphthyl, or the method residing in that the bis-adducts obtained by the Diols-Alder reaction between maleic anhydride and bis-furanic compounds of the general formula WHERE R and R'' have the above-said values, are dehydrated by means of acidic reagents: gaseous hydrogen chloride or hydrogen bromide, concentrated hydrochloric, hydrobromic and sulphuric acids or polyphosphoric acid. The proposed dianhydrides are used for producing polyimides and polyimidazopyrrolones as well as for curing epoxy resins.
Inventors
- 👤 Alfred Anisimovich Berlin
- 👤 Boris Izrailevich Liogonky
- 👤 Boris Isaakovich Zapadinsky
Bibliographic Details
Claims Analysis
Total Claims: 28References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-23 | 1978-12-23 | 1979-06-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-23 | 1982-12-23 | 1983-06-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-23 | 1986-12-23 | 1987-06-24 | $7700.00 | Window Closed / Lapsed |