Bayer Aktiengesellschaft

Helga Rosentreter

Bernhard Wehling

Bernd Makowka

Josef Muller

Heinz-Gunter Klein, Deceased

Gertrud Klein, Heir

Crome tanning of pickled animal hides with a tanning agent comprising a reaction product of a basic chromium (III) sulfate and aliphatic C.sub.4 -C.sub.6 dicarboxylic acids or their salts is improved by preparing the reaction product in an aqueous solution from basic chromium (III) sulfate and 0.2 to 0.8 mol of the aliphatic dicarboxylic acids per mol chromium oxide of the basic chromium sulfate with subsequent adjustment of the theoretical basicity to 0 to 50% with alkali metal hydroxide or carbonate, the reaction product being added to a hide pickling liquor in the form of an aqueous solution having a chromium oxide content of at least 5% or in powder form in a quantity of 0.9 to 1.5% chromium oxide, based on hide weight, with a liquor volume less than 100%, based on hide weight, the final pH value being above 4.0 and the final temperature above 40.degree. C.

High-extraction chrome tanning process

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,

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Leverkusen, Germany

Helga Rosentreter