Abstract

In recent years, organic chrome-free tanning has emerged as an environmentally benign alternative in leather production. However, the high electronegativity of organic chrome-free tanned leather leads to poor binding affinity for anionic dyes and fatliquoring agents, significantly reducing their uptake efficiency. Amphoteric polymer-based retanning agents present an effective solution for chrome-free leather processing by dynamically modulating the surface charge of the substrate, thereby enhancing the uptake and binding affinity of anionic leather chemicals. In this study, two new betaine-containing polymeric retanning-fatliquoring agents were synthesised. First, the intermediate P(LA-co-DM) was prepared by free radical copolymerisation of dimethylaminoethyl methacrylate (DM) and lauryl acrylate (LA), then two products PLDCB and PLDSB were obtained by quaternising P(LA-co-DM) with sodium chloroacetate and 1,3-propane sultone, respectively. The products were characterised by FTIR, ¹H-NMR, and chemical analysis. The application performance of PLDCB and PLDSB in the wet processing of organic chrome-free tanned leather were investigated. The leather treated by PLDCB and PLDSB exhibited better fullness, soft handle, and enhanced mechanical properties with well-dispersed collagen fibres. Specifically, the tensile strength and tear strength of the PLDCB-treated leather were 23.52MPa and 98.69N/mm, respectively. Compared with commercial retanning agents TGR and RVL, PLDCB had better leveling and deepening effect, and the absorption rate of anionic dyes and K/S value of leather were 96.3% and 13.31. PLDCB shows considerable application potential in the wet finishing process of organic chrome-free tanned leather.