Preparation of cationic waterborne polyurethane and its application in leather dyeing

Abstract

The development of organic chromium-free tanning agents is currently a major research focus in leather tanning. However, these agents decrease the electrical potential of the tanned leather, which hampers the absorption of subsequent anionic dyes and fatliquoring agents. Consequently, issues such as lower color fastness, poor dyeing effects and environmental pollution arise. To address these challenges, this study proposes the utilization of anionic polyurethane (CWPU) as a dye fixing agent to enhance its performance and application in the leather preparation process. CWPU was successfully synthesized using polycarbonate diol (PCDL), isophorone diisocyanate (IPDI), polypropylene glycol (PPG), and N-methyldiethanolamine (MDEA) as raw materials, and the optimal synthesis conditions were optimized. The experimental results showed that the synthesized CWPU color fixing agent exhibited excellent emulsion properties and comprehensive performance when the PCDL: PPG ratio was 1:1 and the MDEA addition amount was 6 wt%. When applied to leather color fixation, the leather not only achieved improved dry and wet rubbing fastness levels of 4–5 but also demonstrated significant improvements in solvent wash resistance and perspiration fastness. Furthermore, the leather treated with CWPU color fixing agent exhibited deeper color and improved physical and mechanical properties and tactile quality. Therefore, this study provides an effective choice of color fixing agent for environmentally friendly chromium-free tanning systems and has broad prospects for the application of acid dyes.