Patent ID: 8523957

Claim:
A method of generating reduced anthraquinonoid vat dye composition used in a continuous process of dyeing textile material, said method as implemented in a treatment unit comprising: (a) applying a high concentration anthraquinonoid vat dye composition stored in a plurality of dye tanks into a reaction unit connected to a circulation line of said continuous dyeing process, said dye tanks having a combined volume ≧2000 liters, said reaction unit having a residence/reaction time (RT) that depends on at least anthraquinonoid vat dye half-life and solubility, said anthraquinonoid vat dye concentration in said treatment unit being greater than 80 g/L, said RT and temperature adjusted to achieve a desired ration of reduced-to-unreduced dye; (b) applying at least one reducing agent from a reducing agent tank to said reaction unit having said anthraquinonoid vat dye; (c) effecting isolated reduction of said anthraquinonoid vat dye composition in said treatment unit outside of said circulation line prior to introducing said anthraquinonoid vat dye composition in to said circulation line, said reducing done using said introduced reducing agent to form a reduced anthraquinonoid vat dye; (d) introducing said reduced anthraquinonoid vat dye into said circulation line of said continuous dyeing process only after said step of reducing anthraquinonoid vat dye in said treatment unit wherein dyeing temperature is between 35-45° C. and, following dyeing; (e) oxidizing said reduced anthraquinonoid vat dye by air passage; and, wherein anthraquinonoid vat dye concentration in said treatment unit is lower than feeding dye concentration resulting in no dye precipitation and dye concentration in said treatment unit is higher than circulating dye concentration resulting in effective dye reduction.