Study On Technology Of Painting Enzymatic Unhairing With Low Sulfide

Nowadays leather industry is facing severely environmental and pollutional issues which badly block continual development of leather industry,thus green and clean production is the only way to implement continual development of leather industry. Traditional liming method in unhairing procedure was highly contaminative, enzymatic unhairing was a cleaner method in contrast. However, it was not widely used due to instable quality, complex components and difficult control in the operation. So two sorts of enzyme with higher energy in this paper were introduced to research their depilatory technology, short hair was treated with a few sulfides or peroxides according to hardly dehairing hair. The paper was involved into three parts. Firstly two kinds of proteinase 2709 and A.S1398 were chosen to research their performances, results showed that optimal pH value of 2709 proteinase was about 9, it's energy would drop to low when pH value was greater than 12 and that of 1398 proteinase was 8,it was almost zero when pH was greater than 11. They reached their maximum at 55℃and their energy would sharply drop with temperature elevated; their energy was activable by ions Mn2+ and Ca2+ but restrained by ions Cu2+,Cr3+,Fe2+ and Zn2+. In addition that was slightly activable by detergent.Based on influencing elements of enzyme energy, application conditions of 2709 and A.S1398 proteinases were researched and optimized. Two enzymatic unhairing technologies were obtained including (1) 2709 proteinase pile dehairing technology: 250u/g enzyme 2709 in back parts and 150u/g in belly parts under pH value 9 and (2) A.S1398 proteinase pile dehairing techonolgy: 300u/g enzyme A.S1398 in back parts and 200u/g in belly parts under pH value 7.5, their pile temperatures were all under 25℃. Sulfides and peroxides managed short hairs during process of enzymatic unhairing. Those two methods all reduced environmental pollution. The physical testing of finished leather showed that tearing strength of enzyme treated leather was slightly lower than lime-sulphide treated leather and other indexes were of no difference to conditional method treated leather, but breaking elongation was higher than that of lime treated leather. Through analysis of protein, glucose and hydroproline in waste liquors produced by unhairing procedure and observation of hair and skin during dehairing procedure, results showed that degree of depilation could be expressed by contents of protein and glucose in waste liquors and that of hydrolysis of collagen by contents of hydroproline. Obtained results were consistent to determination of preceding enzyme energy. Otherwise, principle of different unhairing methods and effect of latter procedure on hide could be indirectly explained by observation of hair and skin. Two kinds of enzymatic unhairing methods could not only obtain favorable effect, but also greatly reduce the pollution of sulfide. Physical and mechanical properties of resultant leather were not different from those of liming leather. So it is an effective cleaning unhairing technology method.