Patent · US Expired

Process for the preparation of naphthalene-1,4,5,8-tetracarboxylic acid and its 1,8-monoanhydride in a high degree of purity

US4599431A · kind A · utility

2Cited by

3References

8Claims

0Family size

Assignee

Hoechst GmbH · DE

Inventors

Siegfried Schiessler · Frankfurt am Main, DE
Ernst Spietschka · Idstein, DE

Key dates

Filing date	Jul 5, 1984
Grant date	Jul 8, 1986
Priority date	—
Expiry date	Jul 5, 2004

Classification

Technology area (CPC C)Chemistry; Metallurgy
CPC primaryC07C51/573
WIPO fieldOrganic fine chemistry
WIPO sectorChemistry

Abstract

Process for the preparation of naphthalene-1,4,5,8-tetracarboxylic acid (called "NTC" below) and its 1,8-monoanhydride in a high degree of purity, which comprises dissolving impure NTC or impure NTC-1,8-monoanhydride as the tetra-alkali metal salt of NTC in water in known manner, removing any insoluble impurities present, bringing the clarified solution to a pH value of 4-5 below 45.degree. C., separating off the di-alkali metal salt of NTC which thereby crystallizes out and converting the latter into free NTC or into free NTC-1,8-monoanhydride by treatment with a strong acid at 20.degree. to 100.degree. C.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.