Insights into the Development of Dyeing-Assisting Amphoteric Acrylic Retanning/Fatliquoring Agents for Ecological Chrome-Free Tanned Leather Production

Chrome-free tanning is an emerging trend for the green sustainable development of the leather manufacturing industry. However, conventional anionic wet finishing materials for chrome-tanned leather are not suitable for chrome-free tanning systems due to the imbalance of surface charge between the wet finishing materials and chrome-free tanned leather. In this paper, we have developed a novel and facile approach to synthesizing an amphoteric polymer named PAMLD as a retanning/fatliquoring agent for chrome-free tanned leather. The PAMLD polymer with a suitable particle size (d = 325 nm) and appropriate isoelectric point (pI = 4.6) was prepared by one-step copolymerization in an aqueous solution using acrylic acid (AA), methacrylic acid (MAA), ethyl methacrylate trimethylammonium chloride (DMC), and dodecyl 2-methyl acrylate (LMA) as monomers. The obtained amphoteric polymer was further applied in the wet finishing processing of three types of chrome-free tanned leather. Comprehensive characterizations of leathers treated with PAMLD indicated the retanning and fatliquoring effect of PAMLD on collagen fibers. Moreover, leathers treated with PAMLD exhibited better dyeing properties compared with those treated with the commercial amphoteric wet finishing material (FRA), as evidenced by their superior K/S values and color fastness to rubbing and washing. This research not only provides a feasible approach for preparing multifunctional amphoteric polymers but also offers novel matching wet finishing materials and strategies for variable chrome-free tanned leather production.