Cleaner Processing of Bovine Wet-white: Synthesis and Application of a Novel Chrome-free Tanning Agent Based on an Amphoteric Organic Compound

Wet-white processing is an effective method to reduce or get rid of chrome pollution. However; the current chrome-free tanning agents can't meet the needs both of the market and of environmental protection regarding the aspects of shrinkage temperature, the state of wet-white tanned and clean production. A novel chrome-free tanning agent was synthesized through radical polymerization by employing acrolein and diallyl dimethyl ammonium chloride. Based on this novel chrome-free agent, its characteristics, application and the cleaner processing of bovine wet-white leather were studied in this thesis. The results show that the novel chrome-free agent has the structure of an amphoteric organic compound, appropriate molecular weight and exhibits good tanning properties. The optimal tanning conditions are as follows: the pH value of pickled hide is adjusted to 6.0-7.0, the consumption of the novel chrome-free agent is 5% based on 150% times of the weight of pickle and the pelt is directly tanned for 5 hours at room temperature, then the pH value of the float is adjusted to 7.0-8.0, 100% hot water is added to raise the temperature to 35 degrees C-40 degrees C and the leather is tanned for a further 5 hours. The shrinkage temperature of the leather tanned by the novel chrome-free agent can achieve 86 degrees C or so, and the leather has fine grain and good feel. Based on the performance of the novel chrome-free tanning agent and its tannage, the bated pelt could be tanned directly by adjusting the balance of the formulation, which will greatly reduce the content of chloride ion in the effluent so as to contribute to the clean production of leather.