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Chrome free tanning / R. Celades in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 74 (Année 1990)
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Titre : Chrome free tanning Type de document : texte imprimé Auteurs : R. Celades, Auteur ; J. Duque, Auteur ; J. J. Palma, Auteur Année de publication : 1990 Article en page(s) : p. 170-173 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : The manufacturing processes of leathers and skins are, at the present time, undergoing a change as a result of the demands of environmental pressure groups.
The chrome-free tanning processes such as vegetable, aluminium, and oil do not meet the needs of all the kinds of leather on the market. Present tendencies point to a reduction in the chrome offer or to an exhaustion of the chrome itself. In the light of the environmental tendencies it may well be that, in the future, chromium may be declared a hazardous metal. This event would have serious implications for the tanneries as far as the elimination of waste water and solid waste is concerned.
The solution, we believe, does not lie in reducing the usage of chromium but in the avoidance of its use. In this connection, processes based on synthetic compounds, other metals (copper, zirconium, aluminium, titanium,) aldehyde compounds (glutaraldehyde, formaldehyde, glyoxal, oxazolidines), polysilicic acids, polyamine derivatives and polycarboxylic acids have been reported. The use of chromium, albeit to a small degree, is still necessary in some of these processes.En ligne : https://drive.google.com/file/d/1EEvk1iH2B-wcQCYdBSF_B9pDbGkTOuE_/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8792
in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 74 (Année 1990) . - p. 170-173[article]Réservation
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Titre : The many faces of aging Type de document : texte imprimé Auteurs : V. Candar, Auteur ; J. J. Palma, Auteur ; Y. Eryasa, Auteur ; Ivo Reetz, Auteur Année de publication : 2001 Article en page(s) : p. 35-42 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Cuirs et peaux -- Détérioration
VieillissementIndex. décimale : 675 Technologie du cuir et de la fourrure Résumé : Leather aging can be divided into mechanical, chemical, an dsigns of optical degradation. Mechanical degradation can be accurately followed by measuring the shrinkage of leather, the decay in shrinkage temperature, and the deterioration of tensile strength or tear resistance. Reasons for mechanical degradation can vary : dehydration, scission (the cutting or dividing) of the protein chain or partial detanning. This aging is usually not reversible -only by drastic reprocessing an the pre-aged be reached again.
Chemical changes can include the formation of hexavalent chromium, Cr(VI°, via the oxidation of trivalent chromium. However, in contrast to other forms of aging, this process is both preventable and fully reversible. Other symptoms of chemical aging are the randid odours from aldehyde and ketonic products formed by fatliquor decomposition.
Leather also changes its looks with time. yellowing, which can occur at higher temperatures or under excessive exposure to sun, indicate the formation of conjugated double bounds in fatliquor decomposition products, or in vegetable tannins. On the other hand, fading is a bleaching reaction, where the chemical structure of the dye used is changed.Note de contenu : - THE FATLIQUOR OXIDATION PATH
- IODINE NUMBERS OF FATLIQUORS AND RATE OF AGING : The amount of fatliquor absorbed by the leather - The reactivity of the double bond
- AVOIDING FATLIQUOR OXYDATION : Oil characteristics and processing - Radival scavengers - Reducing agents
- MINIMISING Cr(VI) BY AVOIDING FREE Cr(III)
- Cr(VI) BY DIRECT OXIDATION
- Fig. 1 : Formation of radicals and of hydroperoxides by oxidation
- Fig. 2 : Deterioration of mechanical properties of the leather matrix
- Fig. 3 : Aging for sulfited fish oils with Iodine Numbers of IN 130 and IN 160 (All IN in gl/100g). Aging for 24 hours at 80°C
- Fig. 4 : Cr(VI) values for fatliquors with different absolute IN (IN abd = IN act. conc.). Aging for 24 hours at 80°C
- DOES AGED LEATHER = HIGH C(VI) ?
- Fig. 5 : Cr(VI) formation in various, air saturated crude oils.
- Fig. 6 : Effect of a radical scavenger (RS) on various types of aging. Example of sulfited fish oil. Aging for 24 hours at 80°C
- Fig. 7 : Effect of various reducing agents on aging. Aging for 24 hours at 80°C
- Fig. 8 : Effect of protective auxiliary in comparison with tara. Cr(VI) and shrinkage temp : aging for 24 hours at 80°C
- Fig. 9 : Influence of chromium retannage and washing with complex-active washing auxiliary on extractable Cr(III) and formation of Cr(VI): aging for 24 hours at 80°C.
- Fig. 10 : Aging of leather at 80°C for 24 hours : different degrees of humidityEn ligne : https://drive.google.com/file/d/1-6wBwDhrIJ6Qhy4n7fBxgAdYd5I_8WMC/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=32189
in WORLD LEATHER > Vol. 14, N° 8 (12/2001 - 01/2002) . - p. 35-42[article]Réservation
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