CHROME DYEING USING ANIONIC TRIVALENT CHROMIUM COMPLEXES AS MORDANTS

Chrome dyeings are normally produced by first applying an acid dye con taining ligand groups and then afterchroming with hexavalent chromium derivatives such as dichromate salts. The latter can damage wool fibre s and also are toxic components in dyehouse effluents, so afterchromin g with mixtures of CT(HI) salts and organic acids has been studied. It has been shown that the anionic complexes that form from trivalent ch romium and the organic acids are fibre substantive at pH 2-4 and have the correct stability profile for exchanging ligands to bind the chrom ium with ligand groups in the dye. Dyeings produced generally show col our yields and fastness properties similar to the normal Cr(vl) dyeing process; the exception are these chromophores which undergo oxidative change in the dichromate process.