| 摘要 |
<p>This invention relates to an improved process for the chrometanning of hides to produce leather which comprises the steps of (a) pickling the hide (b) pretanning the hide with a chromium (III) salt, and (c) full tanning the hide with a tanning mixture containing a chromium (III) salt, an acid-binding agent and a polycarboxylic acid or salt thereof, in which the improvement comprises in step (c) at least 1.6 moles per mole of Cr2O3 in the chromium (III) salt employed 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, and wherein the total quantity of Cr2O3 employed in steps (b) and (c) ranges from 1.2 to 2% by weight of the dehaired hide, and step (c) is carried out with up to 100% of the tanning liquor based on the weight of the hide so that the final pH of the liquor is 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 step (b). The invention also relates to a tanning composition useful in this process.</p> |
