| Vat dye has been known as one of the most important dyes and widely applied to fabrics like cotton, wool, silk, hemp, and synthetic or blended fabrics. It has numerous kinds and colors, and its color brightness is satisfying. Since vat dye has superior color fastness to light, heat, solvent and washing, it has also been used in the field of paint, plastic, rubber and dope industry by the type of organic pigment.Ozone which comes from industrial by-product and automobile exhaust exists in the atmosphere of industrial zones or cities. In those cities which are well-developed and owning a large amount of vehicles, the volume of ozone may reach 0.5 ppm to hazard human beings’ lives. The strong oxidizability of ozone can destroy the construction of vat dye, and fades blue jeans dyed. The higher the volume of ozone is, the seriously the dyed cotton fibers of jeans are faded.As yet, how to protect the color of vat dyed fabric in ozone is seldom reported not only in China but also abroad. In our study, methods of improving vat dye’s color fastness to ozone were discussed.Firstly, the mechanism of its fading performance was studied thorough fading experiments. Cotton fabrics were dyed with different kinds of vat dyes. Their fading phenomenon under known concentration of ozone was graded according to the international standard ISO 105/G03—1982. Then the structures of all kinds of vat dyes were analyzed, and the results revealed that the fabrics’ color fastness to ozone was closely associated with the structure of vat dyes.Secondly, alkylphenol and amine were used as reductive compound to enhance the vat dye’s color fastness to ozone. After treated with these reductive compounds the low-grade cotton fabrics’ color fastness were improved greatly. The result showed that it was an effect method for using compound possessing reducibility to protect vat dye from destroying of the strong oxidizability of the ozone.Thirdly, some conclusions have been got from the series of experiment. With the structure of groups which can be easily oxidized, the vat dye is apt to be attacked by the ozone. But when there is a large group near it, the process of oxidation become difficult. The more degree of electronic delocalization is, the more stable the vat dye’s structure is. The structure of the vat dye include heterocycle contained sulphur and heterocyclic ketone, the cotton fabrics dyed by these vat dye are difficult to fade in ozone environment. Amine was proved to be an excellent antioxidant to improve vat-dyed fabrics’ color fastness to ozone. |
