Application of Carboxyl-functionalized Epoxy Resin in the Leather Tanning Process

摘要

Chrome tanning is widely used in the tanning process; however, it can cause environmental pollution. Leather tanned with epoxy resin was considered as a more environmentally friendly process, but it takes as long as five days for reaction, and results in poor performance of leather. The aim of the present study was to tan leather collagen with a carboxyl-functionalized epoxy resin, which was thought to be an eco-friendly tanning process and the reaction time was shortened to 12h. The reaction between carboxyl-functionalized epoxy resin and leather collagen can be divided into two stages, the reaction of epoxy group with leather collagen and the reaction of carboxyl group with leather collagen. The influences of tanning conditions (medium pH, epoxy resin amount and reaction time) on the properties of tanned leather were also discussed. In the first stage, the epoxy group was reacted with leather collagen in basic conditions. The results showed that the carboxyl-functionalized epoxy resin could better penetrate into the leather fibers when the pH value was 8.5, and the best effect of tanned leather collagen was found using reaction condition of pH 7.0. In the second stage, it was the reaction of carboxyl group to leather collagen in acid conditions, and the best effect was found under the condition of pH was 3.5. Meanwhile, it provided a better tanning effect when the carboxyl-functionalized epoxy resin amount was 6% and the reaction time was 12h. The chrome-less tanning process that carboxyl-functionalized epoxy resin combination with 3% chrome was studied. The results showed that the hydrothermal stability and strength properties of leather tanned by carboxylfunctionalized epoxy resin with 3% chrome were close, even superior, to those of the leather produced by conventional chrome tanning with 8% chrome.