| Résumé : |
The object of retannage has changed markedly as a result the still-growing trend towards full grain leather with aniline character. Since finishes with only a slight covering effect are preferred for this kind of leather, not only the fulness, softness, and tightness of grain, but also the fineness of grain, the dyeing properties, and the lightfastness must be regulated via the retanning process. This increased significance of retannage is further accentuated by the fact that the rapidly changing trends of fashion involve not only the shade, but to a rising extent also the handle properties and grain pattern. In order to obtain the properties required, modern leathers must usually be aftertreated more intensively than corrected grain side leather, i.e., with regard to both the quantity of the products and the processing time required.
Some of the properties desirred, such as softness, fineness of grain, and good dyeing behavior, can be obtained by retannage with mineral tanning agents, especially chrome or synthetic. Both methods, however, are limited to the processing of light, thin leathers which are to be varied only in their handle, but not excessively filled. Moreover, purely chrome-tanned leathers are unsuitable for the rapid drying methods usually employed nowadays.
Although the filling effect which some of the individual classes of tanning agents and vegetable tannins, there are often limits set for the application of a filling combination retannage. the use of chrome tanning agents has to be reduced to a minimum in many countries for ecological reasons, and the use of vegetable tannins has to be kept as low as possible because of the high requirements imposed on the fineness of grain or the lightfastness of the leather. If the use of chrome tanning agents is excluded from the retanning process, it is difficult to obtain leathers that are soft and nevertheless have a springy feel, while it is also difficult to retain the fulness and fine grain obtainable by the incorporation of vegetable tannins. This is all the more so, since nowadays also rawstock of relatively poor substance has to be utilized in an optimum way. |
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Latest aspects of retanning full grain leather in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. LXXVI (Année 1981)
