Recent advances in grain damage coverage and color fastness

This work falls into two parts. The first illustrates a method for covering light damage in the dyeing step. The second part details a practical metho d for reactively binding nucleophilic dyes with crosslinking agents. It was found that artificial light damage which simulated light spot could be masked by applying a dye/pigment mixture. Pigments of small particle siz e were chosen which gave the best colour match to the dyes used: Delta E va lues between controls and dye/pigment mixtures were as low as 0.76. Improve ments for Grey Scale contrast between damaged and non-damaged areas could b e improved by up to 2.5 Grey Scale units. Improvements of 1.5 Grey Scale un its were typical. The overall fastness of the pigment dyeings was comparabl e with those of the control dyeings, but better light fastness results were obtained. Work aimed at crosslinking anionic dyes which contained nucleophilic groups studied a range of four crosslinking agents. It was found that each of the se reacted with an amino-functionalised dyestuff in aqueous media. Similarl y reaction of the dye with the crosslinkers during leather processing sugge sted that an offer of 1% crosslinking agent (based on the crust weight) red uces the amount of extractable dye from 75% to about 40%. Significant incre ases in wash, perspiration and wet crock fastness were found with all cross linking agents. Tetrakis(hydroxymethyl)phosphonium sulphate appeared to giv e the best all-round fastness properties.