Bayer Aktiengesellschaft

Helga Heinze

Harro Traubel

Dieter Dieterich

Heinrich Spahrkas

Wolfhard Luck

Klaus Backer

This invention relates to water-soluble, cationic hydrophilic oligourethanes free from isocyanate groups and containing methylol groups and to the use thereof for the tanning, pre-tanning or re-tanning of pelts or pre-tanned leather and as dyeing auxiliaries.

Water-soluble cationic oligourethane resins and the use thereof for the

In the tanning or re-tanning of a hide with a tanning composition comprising a tanning-active substance and at least one of a Cr(III) salt, a dicarboxylic acid, a dicarboxylic acid salt, an emulsifier and an acid-binding agent, the improvement which comprises employing as said tanning-active substance a carboxylic acid carrying at least one of an ester, urethane or amide group. Advantageously the agent has at least two carboxyl groups per molecule and a molecular weight of about 170 to 30,000, preferably 310 to 10,000. The products are softer and better through-tanned and there is maximum utilization of chromium, thereby minimizing the waste disposal problem.

Tanning with carboxylic acid carrying ester, urethane and/or amide group

In the chrome-tanning of hides to produce leather wherein a hide is pickled, pretanned with a chromium (III) salt, and full tanned with a tanning mixture containing a chromium (III) salt, an acid-binding agent and a polycarboxylic acid or salt thereof, the improvement which comprises employing as said polycarboxylic acid or salt thereof at least 1.6 moles per mole of Cr.sub.2 O.sub.3 in the chromium (III) salt employed for full tanning of an aliphatic dicarboxylic acid of 4 to 6 carbon atoms or an aromatic dicarboxylic or tricarboxylic acid containing 8 to 13 carbon atoms or a salt thereof, the total quantity of Cr.sub.2 O.sub.3 employed in pretanning and full tanning ranging from 1.2 to 2% by weight of the hide, full tanning being carried out with up to 100% of the tanning liquor based on the weight of the hide to a final pH of the liquor of at least 3.6. Advantageously, a powder composition comprising additional chromium (III) salt, polycarboxylic acid or salt and acid-binding agent, preferably dolomite, is added after pretanning.

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Cologne, Germany

Helga Heinze