PROCESS FOR PRE-TANNING AND TANNING SKINS WITH ORGANIC TANNING AGENT

摘要

ABSTRACT - 602485 The disclosure relates to a process for pre-tanning skins comprising the steps of: (a) liming and washing the skins; (b) deliming, bating and washing the skins; (c) adjusting the pH, if required; (d) pre-tanning the skins; and (e) adjusting the pH, if required; wherein the step d) of pre-tanning the skins involves treating the skins with: (i) one or more organic tanning agents selected from tetrakis (hydroxymethyl) phosphonium salts, condensates, or derivatives thereof; and (ii) one or more stabilising agents which are oxidizing agents that will oxidise phosphorus from the tanning agent from the +3 to the +5 oxidation state, which may suitably be selected from oxidising agents such as hydrogen peroxide, and alkali metal salts of peroxide, perborate, perchlorate, percarbonate and permanganate, such as sodium or potassium salts thereof, e.g. sodium percarbonate and sodium perborate; wherein the skins are treated with the stabilising agent after being treated with the tanning agent, and wherein the process may comprise the further steps of: (f) piling, grading and packing the skins; (g) shaving the skins; and (h) degreasing the skins. The disclosure also relates to application of the process to methods of tanning, particularly methods of pre-tanning and tanning that do not require a pickling step.