| Résumé : |
Diisocyanates are capable of tanning leather. However, due to their toxicological properties they have never been introduced in the industry technically or commercially. In a 1982 publication, carbamoylsulfonates, derivatives of isocyanates, were mentioned as an alternative to glutaraldehyde in producing wet white. However, the properties obtained, according to the authors of this publication, were technically difficult to obtain due to the major adjustments in pH required. The leathers obtained were very stiff and unacceptable. Leathers of a high quality were obtained in a new experiment by tanning with carbamoylsulfonate. This tanning was carried out at a pH of 6- 8 in the presence of a basifying agent. The leathers had the same quality as leather obtained by an aldehyde tanning, their color was white, the light fastness excellent, and the aging properties were good. By usual retanning, leathers were obtained fitting the properties for use in automobiles. The carbamoylsulfonate tanning eliminates two working steps: pickling and neutralization. Therefore, the waste water of the total tanning process contains a considerable less amount of neutral salts and the working time is reduced as well. Although, the chemicals of the carbam oylsulfonate tanning process are more expensive than aldehyde derivatives, the processing time saved and the reduction of chemicals in the waste water most probably evens out the cost difference. Afterwards, retanning with chrome-III-tanning salts is possible. With special chrome complexes used in the retanning process, a remarkable reduction of dissolved chrome salts in the residual liquor of the retanning (less than 10 ppm Cr) was achieved. It is possible to produce biodegradable leathers by tanning with carbamoylsulfonates. However, the tanning process using carbamoylsulfonates still needs further experimentation to improve the storage stability of the carbamoylsulfonate tanning product itself. Fortunately, storage stable auxiliary products exist which are used in textile sizing that are based on the same chemistry. Therefore, this problem should be easily resolved. This new type of tanning with carbamoylsulfonates may be an alternative to existing tanning processes that currently result in high salt containing waste water. |
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Ajouter le résultat dans votre panierA new approach to tanning - an unconventional attempt in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. C, N° 8 (08/2005)
