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:
Aug. 20, 1991
Filed:
Jun. 19, 1989
Ciba-Geigy Corporation, Ardsley, NY (US);
Abstract
The invention relates to a process for the preparation of concentrated storage-stable aqueous solutions of yellow azo- and azoxystilbene dyes which are obtained by self-condensation of 4-nitrotoluene-2-sulfonic acid in the presence of an alkali metal hydroxide, by converting the sparingly soluble alkali metal salt of the dye into a water-soluble ammonium salt by double cation exchange via a lipophilic ammonium salt, which process comprises carrying out the double ion exchange in a two-phase system of nitrobenzene/water and using, for the first ion exchange a di- or trialkylamine containing a total of 12 to 40 carbon atoms and, for the second ion exchange, a mono-, di- or trialkanolamine containing 2 to 4 carbon atoms in each alkyl moiety. The concentrated storage-stable dye solutions so obtained are particularly suitable for dyeing paper.