Use of NaOH for unhairing hides and the influence of the addition of salts on the process and on the hide properties

The influence of the system containing NaOH, Na2S and a salt such as NaCl, Na2SO4, HCOONa or Na2HPO4 on the properties of hair in the process of unhairing was investigated. The influence of alkaline process conditions such as concentration of NaOH and salt, temperature and duration of the process on the degradation of collagen and non-collagen proteins, the swelling end the quality of unhairing was also studied. It was established that addition of various salts influences the degree of opening up of the dermal structure. This is observed when the amounts of additional salts are not less than 4-5% of NaCl, Na2SO4, HCOONa and 1-2% of Na2HPO4. The unhairing efficiency decreased when these amounts of salts were used with the exception of NaCl. The temperature is of great importance. It must be no more than 30 degrees C. The tendency towards swelling does not follow the tendency to destruction of the collagen. Under certain conditions of the alkaline treatment, the swelling decreases and degradation of collagen increases. The addition of various salts during alkaline treatment widens the range of possibilities of using NaOH for unhairing hides.