Pad Dyeing Of Nanoscale Pigments

Pigment dyeing & printing has several noticeable advantages compared to dyestuffs. These advantages are simple technical process, good light fastness, comprehensive color range, applicability to all fiber types, lower costs, reduced water consumption and reduced impact on effluent etc. Therefore, it has been more and more popular and has great developmental potentialities. However, there are also some disadvantages such as stiffer hand than dyes, reduced brightness, poorer fastness properties to rubbing and so on, which limit its applicability.In this paper, woven cotton fabrics were padding dyed with different color nanoscale pigments-cyan, fuchsin, yellow and black. Two new technologies of nanoscale pigment pad dyeing were investigated. They are two-bath and one-bath pad dyeing processes. The dyeing effect on cotton fabrics was compared with conventional technology.In two-bath dyeing processes, cotton fabric was treated with cationic reagent in the first step in order to impart positive charge to cotton. Then the treated cotton was pad dyed with nanoscale pigment in the second step. The key factors in cationic treatment including the concentration of cationic reagent, pH values of cationic reagent liquid, as well as temperature and time, which affect the cationic degree of cotton fabric were discussed. The optimum application condition of PAE was acquired:50～70g/L of PAE, at pH value 10～11, at 102℃for 2min.The effects of dyeing pH, electrolyte and the concentration of binder on the performance of dyeing were studied. It was found that the uptake of pigment and the color strength(K/S) reached to the maximum in the 9～10 pH value. When the electrolyte concentration was low, the uptake of pigment became increase with increasing salt concentration. But when the electrolyte concentration was high, salt addition could not favor pigment adsorption. The more the binder was added, the better the colorfastness was obtained, but the K/S value did not change. Compared with conventional technology, it was observed that fabrics dyed with the two step technology could get much higher K/S value, more brilliant color but lower rubbing fastness.In the one-bath processes dyeing, the cationic treatment and pigment dying were putted in one process. The key factors including the concentration of cationic reagent, pigment and binder .The effects of concentration of cationic reagent, pigment and binder on the performance of dyeing were studied. The experiment results shown that the better concentration of modification pigment dyeing is 30～40g/L respectively. Compared with the traditional pad dyeing technique of pigment, nanoscale pigment with cationic modification enhanced dye depth and color fastness to crocking and washing, and reduced the dosage of binder.