Dyeing of soybean protein/flax blended yarns with reactive dyes and subsequent dye-fixation

The dyeing process of soybean protein/flax blended yarns with reactive dyes (containing monofunctional or bifunctional groups) and the method of improving the color fastness of dyed yarns treated with an ecofriendly formaldehyde-free fixing agent were studied. Influence factors such as sodium carbonate concentration, salt concentration, fixation time and temperature were analyzed, the optimum processes to soybean protein/flax blended yarns dyed with the two reactive dyes were determined: the soybean protein/flax blended yarns were dyed with Reactive Yellow K-R at a bath to material ratio of 20:1, dye concentration 2% owf., sodium chloride 40 g/L, sodium carbonate 10 g/L, fixed at 85 °C for 30 min; and dyed with Reactive Yellow B-4RFN at a bath to material ratio of 20:1, dye concentration 2% owf., sodium chloride 50 g/L, sodium carbonate 15 g/L, fixed at 70 °C for 50 min. The application processes of formaldehyde-free fixing agent DM-2158 were also determined. Performance test results indicated that both K-type and B-type reactive dyes had good colorfastness to washing and rubbing, and B-type reactive dyes showed a higher fixing effect than K-type reactive dyes. The application of a formaldehyde-free fixing agent to dyed products improved the colorfastness to washing and rubbing, especially for blended yarns dyed with K-type reactive dyes.