Quantitative Determinations of Isoelectric Point of Retanned Leather and Distribution of Retanning Agent

摘要

Neutralized chrome leathers (pH 6.3) were retanned with typical anionic retanning agents acrylic resin (AC), amino resin (AR) and mimosa extract (ME) alone or together. The isoelectric points (pIs) of the retanned leathers were determined using a zeta potential analyzer for solid-state materials, and the penetration as well as the uptake of the retanning agents in the leathers was analyzed using a fluorescent tracing technique. It was found that the pIs of the surface layers of the leathers retanned with 3% of AC, AR or ME alone became below 5.4, while the pIs of their middle layers were still around 7.4. The pis of the upper, the middle and the lower layers of the leather retanned with 3% AC, 3% AR and 3% ME together were very close and below 3.6. Additionally, greater penetrations and uptakes of the retanning agents were obtained after retanning with AC, AR and ME together compared to alone. These results indicate that retanning with more and various anionic retanning agents is very useful for a more thorough decrease in the pI of the chrome-tanned leather and favors the penetration and the uptake of the retanning agents in the leather.