Bleaching and dyeing; fluid treatment and chemical modification – Treatment of hides – skins – feathers and animal tissues – Treatment of untanned skins or hides
Patent
1994-06-02
1996-04-30
Kalafut, Stephen
Bleaching and dyeing; fluid treatment and chemical modification
Treatment of hides, skins, feathers and animal tissues
Treatment of untanned skins or hides
8 9415, 8 942, 8 9421, 8 9424, 8 9425, 8 9426, 8 9427, 8 9428, 8 9429, 8 9431, 8 9432, 8 9433, C14C 108, C14C 0300, C14C 900
Patent
active
055120580
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the treatment of hides, skins or other sheet materials containing collagen, during different stages of the transformation of the skins into leather and different stages of the finishing of said products.
The different stages of the transformation of skins and hides into leather are in particular degreasing, which consists of removing part of the greases from the skin in order to facilitate its transformation into leather and tanning, which transforms the raw, putrescible skin into strong, imputrescible leather. The last mentioned operation is considered to be the most important in the transformation chain of skins into leathers.
The different finishing stages can consist of retanning, which is an operation of reinforcing the mechanical behaviour of leathers, dyeing and waterproofing.
In existing skin and hide treatment processes, these different treatment stages use liquid solvents or aqueous solutions containing active principles, which leads to a large amount of environmentally prejudicial effluents. Moreover, the standards for using liquid solvents are becoming increasingly severe and some of them will be forbidden in the near future.
For example, the quantity of mainly aqueous effluents discharged at present by the leather industry throughout the world is approximately 400 g to 500 million m.sup.3 per year, i.e. close to 40 million "daily inhabitant" equivalents.
The present invention is directed at a process for the treatment of skins, hides or sheet materials containing collagen, which makes it possible to avoid the use of noxious solvents which are prejudicial to the environment and to significantly limit the volumes of effluent produced during said treatments.
The process according to the invention is more particularly applicable to the degreasing and tanning of skins and to the finishing treatments (retanning, reinforcement of the structure, dyeing and waterproofing) of skins, hides and other sheet materials containing collagen.
Thus, the invention relates to a process for the degreasing of skins with a view to the transformation thereof into leather and comprising the following stages: pressure Pi and a temperature Ti, the pressure Pi being at least equal to the critical pressure Pc of the fluid and the temperature Ti being such that the fluid has an adequate density to ensure the partial solubilization of the grease and dense fluid in gaseous form.
Advantageously, in stage a) of said process, there is a continuous circulation of the dense fluid at the pressure Pi and the temperature Ti in a treatment enclosure containing the skins, the dense fluid is purified on leaving the treatment enclosure in order to separate therefrom the dissolved grease and the purified, dense fluid is recycled to the enclosure entrance.
The purification of the dense fluid can take place by varying its pressure and/or its temperature in order to eliminate the dissolved products in liquid form. In order to recycle the dense fluid, it is then necessary to bring it to chosen pressure conditions Pi and temperature conditions Ti.
In stage b), the circulation of the dense, pressurized fluid is interrupted and the enclosure is brought to atmospheric pressure.
In this process, the dense, pressurized fluid is used as the solvent for extracting lipidic grease, but working takes place in such a way that there is not a total grease extraction so as to ensure that the skin retains a supple or flexible appearance.
The use of a dense, pressurized fluid makes it possible to obtain this partial grease extraction, because the solvent and alehydrating properties of the dense fluid can be carefully modified by regulating the pressure Pi and the temperature Ti so as to adjust the density of the dense fluid and obtain the desired skin dilipidation level.
Therefore the process according to the invention makes it possible to perform the degreasing of the skins under good conditions.
The invention also relates to a process for the treatment of products constituted by skins, hides or sheet materials
REFERENCES:
patent: 4776173 (1988-10-01), Kamarei et al.
patent: 5169687 (1992-12-01), Sunol
Carles Maurice
Gavend Gerard
Perre Christian
Vulliermet Bernard
Centre Technique Cuir-Chaussure-Maroquinerie
Commissariat à l'Energie Atomique
Diamond Alan D.
Kalafut Stephen
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