Synthesis and application of comb-like waterborne polyurethane as a dispersant for disperse dyes

Disperse dyes are hardly soluble in water and are usually milled with large numbers of dispersants in the dye industry. A branched waterborne polyurethane (WPU) as a dispersant with different side chain lengths (WPU350, WPU550 and WPU750) was synthesized through an acetone process. The effects of the side chain length on the stability and dispersibility of disperse dyes were particularly discussed and analyzed. The results showed that due to their special comb-like structures, these WPUs were able to achieve good dispersive ability for disperse dyes and WPU550 had the best dispersibility through steric hindrance and electrostatic repulsion on the surface of dyes. In addition, WPU was further employed to prepare the dispersion to dye the polyester fabric. These dispersions with WPU not only demonstrated an improved K/S value, wet and dry rubbing fastness and soaping fastness but also had better dispersing and dyeing performance than commercial dispersants.