Bayer Aktiengesellschaft

Josef Muller

Bernhard Wehling

Heinrich Spahrkas

Wolfhard Luck

Helga Rosentreter

Ernst Komarek

The present invention relates to a process for the retanning (afterchroming) of chrome leathers. It has been found very high chromium exhaustion of the liquor can be achieved if the leather is retanned with mixtures of,

Process for the retanning of chrome leathers

In the chrome-tanning of animal skins and hides by pretanning the pickled pelts with chromium (III) salts, followed by full tanning with chromium (III) salts and acid-binding agents, the improvement which comprises effecting full tanning with the reaction of product at least one of formic acid and a formate with a basic chromium (III) sulphate, at least 2 moles of formate plus formic acid being used per mole of Cr.sub.2 O.sub.3 in the chrome-tanning agent used for full tanning, the total input of chromium oxide being from about 1.0 to 1.8%, based on the weight of the pelts, and tanning being carried out with a liquor volume of at most 100%, based on the weight of the pelts, up to a final pH-value of at least 4.0.

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Leverkusen, Germany

Josef Muller