Process for producing concentrated aqueous solutions of anionic azo dyes
US5508389A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 26, 1993 |
| Grant date | Apr 16, 1996 |
| Priority date | — |
| Expiry date | Mar 26, 2013 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC09B67/0073
- WIPO fieldBasic materials chemistry
- WIPO sectorChemistry
Abstract
If highly concentrated aqueous solutions of azo dyes are prepared directly by diazotization and coupling reactions, appreciable difficulties generally result as a consequence of the fact that the diazotization and coupling reactions give rise to viscous phases which lead to stirring problems in the reaction apparatus used, which in turn results in an incomplete synthesis. The novel process for preparing concentrated aqueous dye solutions of an anionic dye in an aqueous medium overcomes this disadvantage by carrying out the diazotization of the aromatic amine diazo component and/or the coupling reaction between the diazonium salt and the coupling component in the presence of an auxiliary which exerts a viscosity-reducing effect on pasty phases. Examples of such auxiliaries are optionally alkyl-substituted naphthalenesulfonic acid-formaldehyde condensation products, ligninsulfonates, polyacrylates and copolymers of maleic anhydride and methacrylic acid or acrylic acid.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.