The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 27, 1990
Filed:
Nov. 21, 1989
Horst Behre, Odenthal, DE;
Lothar Jakob, Wolfratshausen, DE;
Heinz U Blank, Odenthal, DE;
Dietmar Mayer, Bergisch Gladbach, DE;
Roland Busse, Burscheid, DE;
Bayer Aktiengesellschaft, Leverkusen, DE;
Abstract
The characteristic of the improved process for the preparation of 1,5-dihydroxynaphthalene and 1,5-diaminonaphthalene is to carry out the alkaline pressure hydrolysis of the disodium salt of naphthalene-1,5-disulphonic acid at temperatures from 270.degree. to 290.degree. C. and under 14 to 20 bar using an excess of sodium hydroxide solution such that the molar ratio NaOH/disodium salt of naphthalenesulphonic acid is at least 12:1. The 1,5-dihydroxynaphthalene which is obtained in this manner, without hazard and in substantially higher purity, is then aminated with ammonia in the presence of ammonium bisulphite to give 1,5-diaminonaphthalene, it being possible to achieve a further increase in the degree of purity of the 1,5-diaminonaphthalene by increasing the molar ratio NH.sub.3 /1,5-dihydroxynaphthalene to at least 6:1.