Process for the preparation of concentrated solutions of anionic dyestuffs and dyestuff additives by cation exchange with cation exchange resin
AssigneeBayer Aktiengesellschaft
InventorsJoachim Wolff, Jochen Koll, Karlheinz Wolf, Reinhold M. Klipper, Peter M. Lange
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Abstract
Stable, concentrated aqueous solutions of, in particular, anionic reactive dyestuffs are obtained in a comparatively simple manner by freeing from salts, preferably by means of membrane separation processes, solutions of these substances just as they are obtained in the course of synthesis, and by replacing, with the aid of ion exchangers, the cations which cause sparing solubility.
Claims19
A process for the preparation of concentrated aqueous solutions of anionic dyestuffs and anionic dispersing agents, using as starting materials solutions or dispersions of these substances having a salt content of .ltoreq.5 percent by weight, comprising replacing Na.sup..sym. ions of the dyestuff salts or the dispersing agent salts by Li.sup..sym. and/or NZ.sub.3, in which Z=H or unsubstituted or substituted alkyl, without intermediate isolation of the free acids on which the dyestuffs or agents are based, wherein the cation exchange is carried out by means of cation exchangers in the form of pearls or granules which are insoluble in the reaction medium.
Concentrated solutions which are virtually free from standardizing agents and contain mixed salts of the formula
- [A].sup.m.crclbar. B.sub.r.sup.n.sym. Dp.sup..sym.
- wherein
- A denotes the anion of the dyestuff, or of a dispersing agent,
- B denotes Na, K, Ca or mixtures thereof,
- D denotes H, NZ.sub.3, NZ.sub.4 or Li,
- Z denotes H or an unsubstituted or substituted alkyl,
- m denotes an integer from 1 to 6,
- r/p denotes an integer from 1 to 5, p+r.multidot.n being m, and
- n denotes 1 or 2.
Dependencies are inferred from the claim text.