Process for preparing purified dyestuffs

摘要

The invention relates to a process for the preparation of a purified version of a solvent-soluble dyestuff, comprising the steps of (a) mixing an aqueous presscake of the dyestuff into a water-miscible liquid; and (b) distilling off the water until a water content of 5 % by weight maximum is attained; and (c) filtering the dyestuff composition comprising solvent-soluble dyestuff and water-miscible liquid, thereby removing all insoluble contaminants and (d) diluting the dyestuff composition comprising solvent-soluble dyestuff and water-miscible organic solvent in de-ionized water, thereby performing the precipitation of the solvent-soluble dyestuff which is then isolated after filtration and washing with de-ionized water. This ink jet grade version has the important advantage of being virtually salt-free and solvent-free.