Process for the treatment of skins, hides or shett materials containing collagen by a dense, pressurized fluid

Process for the treatment of products constituted by skins or hides with a view to their transformation into leather, characterized in that it comprises the following stages:

• a) contacting the skins or hides with a dense fluid containing at least one active substance for the transformation of the skins or hides, under a pressure Pi at least equal to the critical pressure Pc of the fluid and at a temperature Ti such that the fluid has an adequate density for impregnating the skins or hides with the active substance or substances and
• b) returning the skins or hides to atmospheric pressure in order to eliminate the dense fluid in gaseous form.

Process for the finishing of leather products, comprising the following stages:

• a) contacting the leather with a dense fluid containing at least one active substance for the finishing of the leather selected from tanning agents, dyeing agents, waterproofing agents acrylate-diisocyanate condensation products, methylol-urea condensation products, methylol-melamine condensation products and precursors thereof, under a pressure Pi at least equal to the critical pressure Pc of the fluid and at a temperature Ti such that the fluid has an adequate density for impregnating the leather with the active substance or substances and
• b) returning the leather to atmospheric pressure in order to eliminate the dense fluid in gaseous form.