Bayer Aktiengesellschaft

Franz Schade

Bernhard Wehling

Bruno Bomer

Joachim Kochta

Reinhard Nebeling

Wilhelm Krummel

Henricus Slaats

Peter Schindlmayr

Herbert Burkhardt

Bruno Zinz

Process for retanning mineral-tanned leathers, characterised in that the retanning agents used are sulphonic acids and/or salts thereof of the general formula ##STR1## wherein R represents hydrogen, --CH.sub.3 or the radicals ##STR2## X represents hydrogen, an alkali metal ion, especially sodium, potassium or lithium ion, or an ammonium ion and

Process for retanning mineral tanned leathers with aromatic sulphonic

In the production of chrome leather, a pretreatment of delimed and bated pelts with condensation products not having a tanning action leads to substrates which, without any problems, can be mechanically dewatered and shaved or split and shaved. The properties of the leathers produced therefrom by chrome tanning do not differ from those of leathers which have been conventionally chrome-tanned and shaved.

Process for producing chrome leather

Terpolymers of 30 to 75% by weight of maleic acid (anhydride), 5 to 60% by weight of (meth)acrylic acid and 5 to 40% by weight of (meth)acrylonitrile are suitable as retanning agents for mineral-tanned leather.

Terpolymers of maleic acid anhydride, (meth)acrylic acid, and

Condensation products which are obtained by co-condensation, in an acid aqueous medium, of terphenylsulphonic acids, naphthalenesulphonic acid, bis-(4-hydroxyphenyl) sulphone and compounds which release formaldehyde are used as tanning agents for the production of leather and as re-tanning agents for re-tanning mineral-tanned leather.

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Bergisch Gladbach, Germany

Franz Schade