Sustainable Indigo Dyeing and Fixation Mechanism of Wet Rubbing Fastness Agent on Cotton Fiber in Silicone Non-Aqueous Dyeing System

Indigo dyeing of cotton fiber in the silicone non-aqueous medium dyeing system was investigated to avoid the multiple dyeing of cotton yarn or fabric, high environmental pollution, and the need for multiple washing and sand washing. After fixing, the rubbing fastness of dyed fiber could be improved to 3–4 grade and the washing fastness increased 1–2 levels. The mechanism of rubbing fastness agents was also studied. Most of the wet rubbing fastness agents for indigo dyeing were waterborne polyurethanes. After fixation, a film was formed on the fiber surface. Moreover, the rubbing fastness was improved by the electrostatic interaction between the cellulosic fiber and indigo after treating with fixing agent. Indigo dyeing of cotton fiber was possible in the silicone non-aqueous dyeing system.