Synthesis and Application of a Low Dye Absorption Waterborne Polyurethane for Microfiber Synthetic Leather

As increasing attention is being paid to harmful residual dye pollution in the dyeing effluent from the microfiber synthetic leather industry, there is an urgent need to explore innovative ways to alleviate such pollution. Here, a low-polarity waterborne polyurethane (WPU) was synthesized using hydroxyl-terminated polybutadiene (HTPB) and polypropylene glycol (N220) as soft segments to react with –NCO on isophorone diisocyanate (IPDI). The structure and properties of modified waterborne polyurethane were characterized by Fourier Transform Interferometric Radiometer (FTIR), and emulsion characterization was performed, including particle size and zeta potential analysis, tensile test, thermal properties test, and contact angle test. The SEM and alkali reduction rate results showed that increasing the HTPB content decreases the alkali reduction rate by blocking the penetration of corrosive ions by the double bond cross-link structure, but higher HTPB addition (>40%) leads to an enhancement in phase separation, which contributes to an increase in the alkali reduction rate. The results of the UV spectrum analysis showed that when the amount of HTPB added was 50%, the coloration rate reached 81.27% compared with 13.18%, which was 68.09% higher than that of the unmodified microfiber leather. The binding of the dry and wet rubbing color of the modified microfiber leather with the addition of 50% HTPB reached grades of 4–5 and 3–4, respectively, which meets most application requirements without subsequent washing.