| abstract |
Process for the preparation of preparations of water-soluble organic dyes, starting from an aqueous salt-containing suspension of the raw dye and using membrane separation processes by the. aqueous suspension of the raw dye is first largely freed of by-products in a first membrane separation process and the salt content is reduced by more than half, the dye suspension is then optionally diluted and then desalinated and concentrated by means of a further membrane separation process and converted into a liquid or solid commercial form. The multi-stage membrane separation process, e.g. Ultrafiltration in combination with hyperfiltration, you achieve a higher membrane flux and avoid malfunctions due to membrane clogging. |