Optimization of the cationizing condition in salt-free reactive dyeing of cotton fabric with the pad-irradiate-pad-steam process using response surface methodology

Response surface methodology is widely used in the optimization of dyeing conditions. Herein, the color strength and dye fixation rate of the cotton fabric dyed by pad-irradiate-pad-steam (PIPS) process were determined and compared to by conventional pad-dry-pad-steam (PDPS) process. Then the response surface methodology and central composite design were used to optimize the cationizing conditions during the pad-irradiation step of the process to obtain high color strength during the subsequent salt-free reactive dyeing of the cotton fabric via a pad-steam process. The obtained experimental data were fitted to the second-order polynomial equation, and response surface plots and contour plots were used to identify the optimal cationizing condition, the 3-chloro-2-hydroxypropyltrimethylammonium chloride concentration of 104 g/L, the microwave irradiation power of 537 W, the treatment time of 6 min, and the molar ratio of sodium hydroxide to 3-chloro-2-hydroxypropyltrimethylammonium chloride of 1.02. The results showed that the experimental color strength of the cotton fabrics was in close agreement with the value predicted by the model and the optimal cationizing condition was obtained precisely.