Ciba Specialty Chemicals Corporation

Elke Polley

Holger Lautenbach

Martina Hoffmann

Jacek Malisz

Rainer Kaufel

Adolf Käser

Adolf K&auml;ser

Described is a process for preparing concentrated solutions or suspensions of anionic organic compounds which comprises a) acidifying an aqueous solution or suspension of an anionic organic compound containing salts and/or impurities to a pH of 4.5 or less, if the pH is above this value, so that b) the anionic organic compound is water-insoluble and precipitates in the form of the free acid, c) bringing the suspension to a salt content below 2% by weight, based on the total weight of the retentate, by means of ultrafiltration with a membrane having pore diameters of from 0.001 to 0.02 &#x3bc;m, and d) optionally washing out the salts with water having a pH below 4,5, e) optionally carrying out acid-free washing with water thereafter, and then f) concentrating, so that the amount of anionic organic compound is 5-50% by weight, and g) if desired, bringing the anionic organic compound into solution by adding an appropriate base.

Process for preparing solutions of anionic organic compounds

Process for the preparation of solutions of anionic organic compounds

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Grenzach-Wyhlen, Germany

Elke Polley