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

Abstract

Chrome tanning is widely used in the tanning process; however,it can cause environmental pollution. Leather tanned with epoxyresin was considered as a more environmentally friendly process,but it takes as long as five days for reaction, and results in poorperformance of leather. The aim of the present study was to tanleather collagen with a carboxyl-functionalized epoxy resin,which was thought to be an eco-friendly tanning process and thereaction time was shortened to 12h. The reaction betweencarboxyl-functionalized epoxy resin and leather collagen can bedivided into two stages, the reaction of epoxy group with leathercollagen and the reaction of carboxyl group with leathercollagen. The influences of tanning conditions (medium pH,epoxy resin amount and reaction time) on the properties oftanned leather were also discussed. In the first stage, the epoxygroup was reacted with leather collagen in basic conditions. Theresults showed that the carboxyl-functionalized epoxy resincould better penetrate into the leather fibers when the pH valuewas 8.5, and the best effect of tanned leather collagen was foundusing reaction condition of pH 7.0. In the second stage, it was thereaction of carboxyl group to leather collagen in acid conditions,and the best effect was found under the condition of pH was 3.5.eanwhile, it provided a better tanning effect when thecarboxyl-functionalized epoxy resin amount was 6% and thereaction time was 12h. The chrome-less tanning process thatcarboxyl-functionalized epoxy resin combination with 3%chrome was studied. The results showed that the hydrothermalstability and strength properties of leather tanned by carboxylfunctionalizedepoxy resin with 3% chrome were close, evensuperior, to those of the leather produced by conventionalchrome tanning with 8% chrome.