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Services: Scouring Carding Combing Dyeing |
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DyeingProducts from wool fibers are, at different phases of their processing, dyed practically entirely employing periodic methods. The used groups of dyes are: acidic, acidic chromic, metal - complex 1:1 and 1:2, reactive. Dyeing with acidic dyes is proceeded in acidic surrounding, whereas the range of dyebaths is much more varied depending on the type of an acid dye. The lower the affinity with wool fibers the dye molecules show, the stronger acidic surrounding (lower pH) must be created to achieve proper conditions for the sorption of the dye. For that reason organic acids are used, formic and acetic, as well as acid - forming salts (e.g. ammonium sulphate). In order to achieve even stain effects, fixing agents, which are usually either anionic or nonionic surfactants, must be added to the dyebaths. Wool dyeing with acidic chromic dyes involves two crucial phases, in a given order: - the first one is product treatment in the dyebath, which aim is diffusion of the dye molecules into the textile material; - the second one, called (chromium) afterplating, is carried out by applying either sodium or potassium dichromate to the exhausted dyebath (after the end of the first phase). The aim of this after - treatment is to create complex bonds in a fiber with chrome cation Cr +3, which guarantees a great fastness of stain effects. Dyeing with metal - complex dyes 1:1 is carried out in conditions of great acidity of the dyebath, in presence of sodium sulphate and fixing agents. Usage of metal - complex dyes 1:2 does not demand such a strong acidic surrounding; pH 5 - 7 range is obtained from acetic acid and ammonium acetate. |
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