Research progress of cotton indigo dyeing mechanism

Based on the structure and property of indigo dye,cotton yarn indigo dyeing mechanism is discussed.The indigo single molecule is simple in structure and the crystal structure shows the plate-shape.Indigo is of high stability and excellent biological safety.Indigo is insoluble in water and can be converted into water-soluble by use of reducing agent and alkali and can exist as four species in the dye bath of which the mono-sodium phenolate form of reduced indigo is the most suitable for dyeing cotton yarn.When the dye bath pH is 11,the color yield of indigo on denim yarn can reach the greatest and the cotton yarn shows distinct ring dyeing effect.Adding the number of dips at room temperature and air oxidation in indigo dyeing,color yield on cotton yarn can be improved.