One-step approach to fabricating amphoteric polymer fatliquors for chrome-free tanned leather eco-manufacturing

The leather manufacturing industry is increasingly embracing chrome-free tanning methods to promote environmental sustainability. However, the transition to chrome-free tanning systems presents a notable obstacle: the incompatibility of traditional anionic wet finishing materials with chrome-free tanned leather due to differences in surface electrical behavior. Herein, an amphoteric polymer, referred to P(AA-co-DMAEMA-co-DA), was synthesized through a simple one-step free radical copolymerization using acrylic acid (AA), dimethylaminoethyl methacrylate (DMAEMA), and dodecyl acrylate (DA). Notably, the isoelectric point of P(AA-co-DMAEMA-co-DA) is 7.7, which contributes to improving the leather's positive electric property and enhancing the binding between the amphoteric polymer fatliquors (APF) and collagen fiber. The APF achieves a remarkable absorption rate of 96.2% and a dyeing uptake rate of 94.3% for anionic dyes, resulting in a uniformly bright surface color of the dyed leather and further significantly reducing the dye usage. Overall, the comprehensive properties of APF align with the electrical origins of organic chrome-free tanning leather, exhibiting a pronounced fatliquoring effect while reducing the dye content in the waste liquor. This contribution holds promise for advancing chrome-free tanning technology toward greener environmental practices.