Cationic superfine pigment dyeing for wool using exhaust process by pH adjustment

Abstract

The cationic superfine pigment is prepared using octadecyl dimethyl benzyl ammonium chloride as dispersing agent in order to enable the pigment to dye wool through an exhaust process. Pigment uptake, color strength (K/S value), fastness properties, and penetration were measured. The results show that cationic superfine pigment can be adsorbed on wool under different pHs. Not only dyebath pH but also dyeing time and pigment dosage are found to be closely related to K/S value. The increase of pH results in high pigment uptake and K/S value which increases rapidly beyond or at isoelectric point (PI) of wool. Dry and wet rubbing fastness are improved with the increase of binder dosage, achieving 3 and 3–4 grade respectively as binder amount increases up to 40 % o.w.f. Wool yarns dyed by cationic superfine pigment present better light fastness over 5 grade than those treated with acid dyes. According to micrographs of cross-sections, the distribution of pigment particles on wool fibers shows loop dyeing. It has been demonstrated that it is feasible for cationic superfine pigment to dye wool by pH adjustment.