GB1170801A - Improvements in or relating to the depilation of animal hides - Google Patents

Abstract

1,170,801. Depilating, bleaching and tanning or tawing hides and skins. FARBWERKE HOECHST A.G. Feb.27, 1967 [Feb.25, 1966], No. 9194/67. Addition to 1, 049, 706. Heading C6C. The process according to the main invention is improved and expedited in that keratin-containing parts, such as epidermis, hairs, wool and scales, are removed from soaked or moist hides, pelts and skins, e.g. snake skins (all hereinafter referred to as hides) by subjecting them, e.g. in a revolving drum, to the action of chlorine dioxide until said parts have become jellified and softened, and then to treatment with an alkaline, aqueous liquor having a PH of at least 7À5, preferably above 8À0, or alternatively to treatment with gaseous ammonia, until said parts are loosened and detached from the hides. Preferably, chlorine dioxide gas free from oxygen is used, e.g. chlorine dioxide mixed with an inert gas, such as nitrogen or carbon dioxide, to reduce the risk of an explosion. The chlorine dioxide gas may be produced by the action of concentrated sulphuric acid on an alkali metal chlorate, or by reacting chlorous and nitrous acids. A mixture of chlorine dioxide and carbon dioxide may be generated by reacting chlorous and oxalic acids. The chlorine dioxide may be generated in situ from a substance which furnishes chlorine dioxide, such as sodium or potassium chlorite, in a paste or an acidified, aqueous depilating liquor having a pH between 1À5 and 3À5, which liquor may contain a baffer salt, such as sodium dihydrogen phosphate, sulphate or acetate. Depilation may be completed and bleaching may be effected by treating the hides, in an acidic liquor, with more chlorine dioxide. The depilated and bleached hides may be chrome-tanned or alumtawed.