Abstract

A new tetrakis hydroxymethyl phosphonium sulphate (THPS)-zirconium combination tanning system has been developed. The optimum dosage of THPS, pickling pH and basifying pH were 2.0%, 3.5 and 5.0, respectively. The amount of THPS and zirconium sulphate were optimized at 2.0% and 2.5% (based on the pelt weight). The influence of ligands on the shrinkage temperature (Ts) of leathers has also been studied and the Ts of THPS alone and THPS-zirconium combination tanned leathers were above 85°C and 95°C, respectively. Colour fastness to dry/wet rub of THPS-zirconium combination tanned leathers was much better than the relevant colour fastness to dry/wet rub of THPS alone tanned leathers.

Scanning electron microscopic studies show that the fibre weave of THPS-zirconium combination tanned leather was much closer than for THPS only tanned leather and the fibre weave of THPS-zirconium combination tanned leather was closer with an increase of amount of zirconium sulphate. Hence, this proves that the softness was reduced with an increase of the amount of zirconium sulphate and that the reactivity of zirconium sulphate with collagen fibre was very strong. The bulk trial carried out in Haining Shangyuan Leather Co., Ltd., proved that all indexes of the leather reached Chinese standard requirements.