Preparation of aqueous concentrates of yellow azo and azoxystilbene dyes utilizing alkanolamine salts
US5041539A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 19, 1989 |
| Grant date | Aug 20, 1991 |
| Priority date | — |
| Expiry date | Jun 19, 2009 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC09B67/0073
- WIPO fieldBasic materials chemistry
- WIPO sectorChemistry
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.