Process for tanning hides.

摘要

A process for tanning hides for soles or insoles with ammonium titanyl sulphate. The hides, subjected to soaking, liming, fleshing and deliming, are first treated with ammonium sulphate. Successively, ammonium titanyl sulphate as well as citric acid or an alkali metal citrate are gradually added to the bath, while maintaining the bath temperature at a value not exceeding 37 ° C and the bath pH at from 1.7 to 2.5. After each addition, the hides are treated until they have absorbed at least 90% of the soluble Ti (IV). Sodium sulphite and hexamethylenetetramine are then gradually added; this addition is such as to bring the final pH of the bath to 3.8 - 4.5 and to exhaust the bath of soluble Ti (IV). NaHC0<Sub>3</Sub> is then added until a pH value of the bath from 4.9 to 5.0 is reached, such pH being maintained for at least 2 hours. At least one tanning treatment with a tannin, either prior to the treatment with ammonium titanyl sulphate (pretanning), or after the treatment with NaHC0<Sub>3</Sub> (additional tanning) is carried out, such tanning being carried out with a synthetic or vegetable tannin in the former case, and with a synthetic tannin and/or rubber-like polymer in the latter case.