Chrome-Reduced Combination Tanning for Cleaner Dyed Sheep Fur Processing

Abstract

Chrome tanning is essential for conventional processing of dyed sheep fur as it can provide fur with high hydrothermal stability suitable for dyeing of wool at a temperature around 70°C. However, a long float length and a big offer of chrome tanning agent (16 g/L) are required for the tanning process, which lead to poor uptake of chrome and excessive discharge of chrome in wastewater. In this study, reduction of chrome offer in dyed sheep fur production was investigated to develop a cleaner tanning technology. It was found that the even distribution of chrome and satisfactory dispersion of fur collagen matrix were achieved even though chrome tanning agent offer was reduced to 2 g/L and 4 g/L. But the shrinkage temperature of the furs was only 79°C and 85°C, respectively, which resulted in a sharp area shrink of fur in following high temperature dyeing. In the combination tannage using 10 g/L amphoteric organic tanning agent (TWT) and 2 g/L or 4 g/L chrome tanning agent, the shrinkage temperature of fur was higher than 90°C accompanied by a higher utilization of chrome. These combination tanned furs were capable of enduring dyeing process at 68°C for 8 h, and presented a high uptake of post tanning chemicals because they had an isoelectric point close to that of chrome tanned fur. More importantly, the physical properties of the combination tanned dyed furs were comparable to the dyed fur made by conventional chrome tanning using 16 g/L chrome tanning agent.