Preparation of stable anionic dyestuff solutions: pressure permeation of crude dye in solution of lithium or ammonium salt
AssigneeBayer Aktiengesellschaft
InventorsMartin Michna, Hans-Werner Zillger, Dietrich Tegtmeyer
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Abstract
Stable aqueous solutions of anionic dyestuffs, preferably reactive dyestuffs, are obtained at very low costs by pressure permeation, if the feed solution for the pressure permeation is prepared by stirring the optionally dried presscake or the suspension of the crude dyestuff in an electrolyte solution.
Claims6
Process for the preparation of stable aqueous solutions of anionic dyestuffs by pressure permeation of feed solutions of the crude dyestuffs, characterized in that the feed solution for the pressure permeation is prepared by stirring an optionally dried presscake of the crude dyestuff or a suspension of the crude dyestuff into an electrolyte solution containing 0.1 to 20% by weight of lithium salts or ammonium salts of organic or inorganic acids.
Dependencies are inferred from the claim text.