VERFAHREN ZUR HERSTELLUNG VON PRAEPARATEN WASSERLOESLICHER ORGANISCHER FARBSTOFFE.

摘要

A process for the preparation of formulations of water-soluble organic dyes starting from an aqueous salt-containing suspension of the untreated dye and using membrane separation methods, which process comprises substantially freeing the aqueous suspension of the untreated dye from by-products and reducing the salt concentration by more than half in a first membrane separation treatment, then diluting the dye suspension in a further optional step and effecting deionization and concentration in a second membrane separation treatment and converting the concentrate so obtained into a liquid or solid commercial formulation. This multi-step membrane separation process, e.g. ultrafiltration combined with hyperfiltration, results in a high rate of permeation through the membrane and avoids operating problems caused by membrane clogging.