Sustainable fatliquoring for chrome and chrome-free leather using amphoteric copolymers

Abstract

In pursuit of environmentally sustainable leather processing, this study reports a novel amphoteric copolymeric fatliquor synthesized from allyltrimethylammonium bromide (ATMA) and dimethylaminoethyl methacrylate (DMAEMA) through free radical copolymerization. The copolymer exhibits a dual ionic character that ensures compatibility with both chrome-tanned and chrome-free leather systems. Structural characterizations using FTIR, NMR, GPC, and ESI-MS confirmed the successful incorporation of cationic, anionic, and hydrophobic functionalities. The amphoteric architecture facilitated pH-responsive interactions with collagen, promoting uniform penetration and efficient fixation. In chrome-tanned leather, the copolymer achieved a substantially higher fatliquor uptake (85.2%) compared to conventional systems (68.7%), along with an improved shrinkage temperature (112 °C vs. 103 °C) and tensile strength (32.25 N/mm², making a 46.7% increase). Enhanced softness and fullness were also observed, with a softness index of 8.3 compared to 6.1 for the control. Notably, the effluent chemical oxygen demand decreased from ~ 42,000 mg/L to ~ 32,000 mg/L, indicating a lower environmental burden. Comparable improvements were observed in chrome-free leather, demonstrating the copolymer’s versatility across tanning systems. This work not only presents a scalable and eco-efficient fatliquoring technology, but also provides a fundamental advancement in understanding collagen-copolymer interactions that significantly contributes to the goals of sustainable leather manufacturing.

Graphical Abstract

Keywords

Amphoteric copolymer / Collagen interaction / Chrome-free tanning / Fatliquoring / Effluent reduction / Eco-friendly leather processing

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Funding

Mission mode project on Speciality chemicals(MMP035201)

RIGHTS & PERMISSIONS

The Author(s)