Complex Chromogen Systems Applied on Leather

The restrictions included in the environmental legislation have oriented the leather dyes market toward metal-complex dyes class with lower ecological impact. The main aim of the paper was to obtain new acid azo (1:2) metal-complex dyes, conditioned in ecological microgranular form, with good physico-chemical and coloristic performances, with a minimum impact on the environment and on the human health. The synthesized metal-complex dyes are based on o,o’-dihydroxy-azo system and they are dyeing leather in ruby, reddish-violet, violet, blue, olive and gray shades. The synthesis involved specific processes like diazotizing, coupling, complexing, filtration, drying and grinding. The conditioning of the synthesized dyes was achieved by micro-granulation in order to obtain a new commercialized presentation form. For experiments raw materials were used with reduced eco-toxicological risks. We've obtained acid azoic (1:2) symmetrical and asymmetrical metal-complex dyes; metal is chromium or cobalt. The new structures were analyzed by specific physico-chemical methods (e.g., thin layer and column chromatography, atomic emission spectrometry, absorption spectroscopy in UV-VIS range, VIS spectrophotometry) and the leather dyeing by the well known coloristic standardized tests (light fastness, moist and drying rubbing fastness, water drop fastness, dyeing appearance, penetration degree, inorganic and organic acids fastness, alkali fastness, hard water fastness, dye solubility). The results allow us to appreciate that doesn’t exist significant differences between coloristic performances of the conditioned (in microgranules form) and unconditioned dyes (in dust form). The new dyes have applicative performances at the level of the actual marks marketed in the world.