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Vegetable tannage : Where do the tannins go ? / E. Haslam in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 81, N° 2 (03-04/1997)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 81, N° 2 (03-04/1997) . - p. 45-51 Titre : Vegetable tannage : Where do the tannins go ? Type de document : texte imprimé Auteurs : E. Haslam, Auteur Année de publication : 1997 Article en page(s) : p. 45-51 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Cuirs et peaux Tannage végétal Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Man has used vegetable tannins to convert animal hides to leather for many thousands of years. Leathermaking with vegetable tannins remains because, among other reasons, it occupies a small but important niche in the market and because it still offers a challenging blend of chemistry and art. Notwithstanding this long history the molecular mechanisms which underlie vegetable tannage are still not clear. Ideas concerning the mechanism of vegetable tannage were conceived and developed some 40-50 years ago and they have remained essentially unchanged inthe intervening years. They reflect the status of the fundamental chemistry of collagen, (the principal protein in animal skins), and the vegetable tannins at that time. It is therefore both timely and important to review these ideas in the light of the discoveries made during the past 20 years, not only in relation to the structure of the vegetable tannins and the forces which drive their complexation with other molecular species, buty also, and more particularly, against the background of the very detailed knowledge which has now emerged, principally from physiology and medicine, concerning the structure of the collagen molecule, collagen fibrils and collagen fibres. Individual collagen molecules may thus be regarded as stiff rod-like molecles whose staggered form of organisation in the collagen fibre gives rise to a liquid crystal-like supramolecular assembly containing "holes" or "gap zones". The essence of tannage is stabilisation of the protein structure by the incorporation into the collagen fibril structure and immobilisation therein of substances (tannins) which have an affinity for various functional groups in the protein structure. This background is used to develop new ideas on the mechanism of vegetable. En ligne : https://drive.google.com/file/d/1I6eT7ZforjMQ5vsVBDVZjf457i_7bReR/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8052 [article]

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Investigation of the reductive metabolism of the azo dye "coriacide black SB" in rats / M. K. Ellis in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 81, N° 2 (03-04/1997)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 81, N° 2 (03-04/1997) . - p. 52-56 Titre : Investigation of the reductive metabolism of the azo dye "coriacide black SB" in rats Type de document : texte imprimé Auteurs : M. K. Ellis, Auteur ; G. J. McPherson, Auteur ; N. Ashcroft, Auteur Année de publication : 1997 Article en page(s) : p. 52-56 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 547.86 Colorants et pigments Résumé : Azo colorants may undergo in vivo reduction of the azo group to release amines, some of which, through subsequent metabolic activation, are considered to be carcinogenic. Thus, all azo colorants whose metabolism can potentially liberate a carcinogenic amine are suspected of having a similar carcinogenic potential. Chemical methods used to assess the likely production of such amines use reductants such as sodiumdithionite or Raney Nickel. A recent investigation of the applicability of the use of these strong chemical reductants to force azo fission questions their suitability for certain classes of azo colorants. In particular potentially non-carcinogenic aniline-based azo dyes were found to release trace amounts of the known human carcinogen 4-aminodiphenyl, even though this amine is absent before reduction. To assess the potential for the enzymatic formation of 4-aminodiphenyl in vivo, we have compared the reductive biotransformation of the aniline-azo-linked dy Coriacide Black SB with that of a 4-aminodiphenyl-azo-linked analogues in rats. 4-Aminodiphenyl could not be detected in the urine of rats administered Coriacide Black SB, whereas this amine was detected in the urine of rats administered the 4-aminodiphenyl-azo-linked analogue. This finding suports evidence that the 4-aminodiphenyl detected following the chemical reduction of dyes incorporating aniline as the azo component is an artefact of the reduction conditions and would not occur in vivo. En ligne : https://drive.google.com/file/d/1P5d-vIaYieQupED9WZg3_PgMBhdrr0Cl/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8053 [article]

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Use of NaOH for unhairing hides and the influence of the addition of salts on the process and on the hide properties / Virgilijus Valeika in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 81, N° 2 (03-04/1997)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 81, N° 2 (03-04/1997) . - p. 65-69 Titre : Use of NaOH for unhairing hides and the influence of the addition of salts on the process and on the hide properties Type de document : texte imprimé Auteurs : Virgilijus Valeika, Auteur ; J. Balciuniene, Auteur ; Kestutis Beleska ; A. Skrodenis ; V. Valeikienè Année de publication : 1997 Article en page(s) : p. 65-69 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : The influence of the system containing NaOH, Na2S and a salt such as NaCl, Na2SO4, HCOONa or Na2HPO4 on the properties of hair in the process of unhairing was investigated. The influence of alkaline process conditions such as concentration of NaOH and salt, temperature and duration of the process on the degradation of collagen and non-collagen proteins, the swelling and the quality of unhairing was also studied. It was established that addition of various salts influences the degree of opening up of the dermal structure. This is observed when the amounts of additional salts are not less than 4-5 % of NaCl, Na2SO4, HCOONa and 1-2 % of Na2HPO4. The unhairing efficiency decreased when these amounts of salts were used with the exception of NaCl. The temperature is of great importance. It must be no more than 30°C. The tendency towards swelling does not follow the tendency to destruction of the collagen. Under certain conditions of the alkaline treatment, the swelling decreases and degradation of collagen increases. The addition of various salts during alkaline treatment widens the range of possibilities of using NaOH for unhairing hides. En ligne : https://drive.google.com/file/d/1BfVgJjT0zJ7Xeo0SuMWdQWAc6-xDDgzj/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8054 [article]

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Liming process using hydrogen peroxide / Josep Maria Morera in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 81, N° 2 (03-04/1997)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 81, N° 2 (03-04/1997) . - p. 70-73 Titre : Liming process using hydrogen peroxide Type de document : texte imprimé Auteurs : Josep Maria Morera, Auteur ; Esther Bartoli, Auteur ; M. Dolors Borras, Auteur ; D. Munoz, Auteur ; F. J. Jiménez, Auteur ; Agusti Marsal, Auteur Année de publication : 1997 Article en page(s) : p. 70-73 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : In this work, the feasibility of an oxidative liming process with hydrogen peroxide in alkaline medium was studied. The possible reduction in water consumption by float recyclinbg and in effluent loadings by precipitation and separation of proteins contained inthe liming effluents were also investigated. On the basis of preliminary trials, a second order central rotatable design as a function of both the hydrogen peroxide offer and the mechanical action of the drum, was applied to detemrine the variation of selected physical properties of chrome leather previously subjected to the oxidative liming process. This process was compared with a conventional liming process with sodium sulphide and calcium hydroxide. Subsequently, a study on the quantification of water consumption as well as analyses of COD, soluble solids and suspended matter of the resulting wastewater were carried out for a given hydrogen peroxide offet and drum mechanical action. En ligne : https://drive.google.com/file/d/16-g98ChCQaqwB-yjvGACvAsbXrMuf93F/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8055 [article]

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