The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 12, 1989
Filed:
Jul. 25, 1988
Christiane Hartling, Schopfheim-Fahrnau, DE;
Alberto Rabassa, Oberwil, CH;
Ciba-Geigy Corporation, Ardsley, NY (US);
Abstract
The continuous workup of aqueous crude dye suspensions is carried out in a multi-stage membrane separation unit by feeding into each membrane separation stage a dye suspension and also wash water, permeate from the subsequent membrane separation stage or a mixture consisting of wash water and permeate. A separation into retentate (concentrate) and permeate takes place, in which the degree of concentration and the degree of desalting in each membrane separation stage is controlled by means of a suitable variable, for example the conductivity or the volume of the permeate in each case or the concentration of the retentate. This control allows the reproducible preparation of dye formulations having constant properties and, due to the optimization of the volume streams, leads to a significant reduction in water pollution.