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Interaction between amphoteric polymer and silicic acid tanned leather : Ingenious regulation of ph based on isoelectric point / Ze Liang in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CXVIII, N° 10 (10/2023)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CXVIII, N° 10 (10/2023) . - p. 403-416 Titre : Interaction between amphoteric polymer and silicic acid tanned leather : Ingenious regulation of ph based on isoelectric point Type de document : texte imprimé Auteurs : Ze Liang, Auteur ; Zetian Zhang, Auteur ; Yang Liu, Auteur ; Zhengjun Li, Auteur Année de publication : 2023 Article en page(s) : p. 403-416 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Caractérisation Composés amphotériques Cuirs et peaux -- Propriétés physiques Huile de ricin et constituants Point isoélectrique En biochimie, le point isoélectrique (pI) ou potentiel hydrogène isoélectrique (pHI) est le pH auquel une molécule est sous forme d'ion mixte ou, en physico-chimie, le pH d'une solution aqueuse dans laquelle un solide existe sous un potentiel électrique neutre. En physico-chimie : Selon Bolger, le caractère acide ou basique d'une surface s'exprime par son point isoélectrique " Is ou IEPS (Iso Electric point for the surface) " ou point de charge nulle " PCN ou PZC (Point of Zero Charge) ", défini comme étant le pH de la solution aqueuse dans laquelle le solide existe sous un potentiel électrique neutre. Si le pH de la solution est basique, la surface est acide, et inversement. La différence entre le PZC et l'IEPS est basée sur le phénomène d'adsorption spécifique. On peut considérer que si la grandeur mesurée ne dépend pas de la solution utilisée pour la mesurer (pH, concentration, nature des ions), alors on a affaire à un PZC. Dans le cas contraire, c'est un IEPS que l'on mesure. Par exemple, quand la mesure de goutte sessile à deux liquides est utilisée, on considère en général qu'il n'y a pas adsorption des ions de cette goutte et que la goutte déplace complètement l'alcane qui sert de deuxième liquide: on est alors en présence d’un PZC. Au contraire, dans les mesures de potentiel d'écoulement (streaming potential), la solution joue un rôle important et c'est un IEPS que l'on mesure. Enfin, la charge nette se définit grâce au pH de la solution aqueuse dans laquelle la surface métallique existe, dans un état électriquement neutre (c’est-à-dire [M-OH2+ surf]=[M-O- surf]) et au PZC. - Si pH < PZC alors la charge nette est positive - Si pH > PZC alors la charge nette est négative. Il existe plusieurs méthodes expérimentales permettant de décrire l’état acido-basique de la surface : la mesure du potentiel d’écoulement, la photoélectrochimie, la mesure de l’angle de contact, et la spectroscopie XPS. Polyaddition Polymères -- Synthèse Polymères en émulsion Produits de nourriture du cuir Silicique, Acide Tannage Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Silicic acid-based tanning system is an effective and promising chrome-free tanning technology, and it is urgent to develop compatible post-tanning processes. Fatliquoring is one of the key procedures to determine the quality of resulted leather and fatliquoring agents mainly play the role of an effective softer/ plasticizer in leather production. However, there is a mismatch between most commercial fatliquoring agents (mainly compatible with chrome tanned leather) and silicic acid tanned leather (named SATL). Herein, an amphoteric polymer emulsion (APE) was prepared by free radical polymerization using methacryloxyethyl trimethyl ammonium chloride (DMC), 2-acrylamido-2-methylpropanesulfonate (AMPS), lauryl methacrylate (LMA), dimethylaminoethyl methacrylate (DMAEMA) as monomers. And in order to improve the lubricating property, APE was further compounded with castor oil to obtain an amphoteric fatliquoring agent (named COAPE). Comprehensive characterization showed that the amphoteric (pI=8.22) and amphiphilic APE could reduce the surface tension of water to 38.6 mN/m. The fatliquoring process was controlled by ingenious regulation of pH based on isoelectric points (pIs) of APE and SATL. In the initial stage, the pH of the bath was adjusted to be lower than the pIs of APE and SATL, amphoteric polymer molecules could easily penetrate into SATL leather as they are all positively charged. While during the fixing stage, the pH of the bath was adjusted between the pIs of APE and SATL, so the electrostatic interaction between amphoteric polymer molecules and SATL leather, as well as the aggregation of amphoteric polymers can promote their combination synergistically. As a fatliquoring agent, the application of COAPE demonstrated that its absorpotion rate (90.5%) was much higher than anionic commercial fatliquoring agent (63.2%), thus imparting SATL leather better softness (6.5 mm), elongation at break (95.5%) and tensile strength (11.6 N/mm2). These findings therefore provided scientific basis and technical support for the application of amphoteric materials to silicic acid-modified collagen matrix and would promote the practical application of silicic acid-based chrome-free tanning technology. Note de contenu : - EXPERIMENTAL : Materials - Synthesis of amphoteric polymer emulsion (APE) and amphoteric fatliquoring agent (COAPE) - Characterization and properties of APE and the amphoteric polymer - Application of APE and COAPE in leather fatliquoring process - RESULTS AND DISCUSSION : Characterization and properties of APE and the amphoteric polymer - Insight into interaction between amphoteric polymer and silicic acid tanned leather - Table 1 : Fatliquoring process - Table 2 : Fatliquoring agent and pH value of bath liquid used in different fatliquoring schemes - Table 3 : Physical properties of SATL leather treated with different fatliquoring agents DOI : https://doi.org/10.34314/jalca.v118i10.8229 En ligne : https://drive.google.com/file/d/13AQaPMWZmhlaEeSA3efdY8mtnqf7Tuiw/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=39939 [article]

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Biomass-based tanning agent for sustainable leather manufacture via cyanuric chloride modified chitooligosaccharide / Min Jiang in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CXVIII, N° 10 (10/2023)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CXVIII, N° 10 (10/2023) . - p. 417-427 Titre : Biomass-based tanning agent for sustainable leather manufacture via cyanuric chloride modified chitooligosaccharide Type de document : texte imprimé Auteurs : Min Jiang, Auteur ; Yuanhang Xiao, Auteur ; Jun Sang, Auteur ; Chunhua Wang, Auteur ; Jiajing Zhou, Auteur ; Wei Lin, Auteur Année de publication : 2023 Article en page(s) : p. 417-427 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Agents de tannage Analyse morphologique Biomasse Caractérisation Chitooligosaccharide Composés organiques -- Synthèse Cuirs et peaux -- Propriétés organoleptiques Cuirs et peaux -- Propriétés physiques Poids Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Developing alternative tanning agents to avoid the potential environmental and human health risks from the conventional chrome tanning is essential for the leather industry. In this work, we prepared an eco-friendly biomass-based tanning agent dichlorotriazinyl chitooligosaccharide (DTCS) by modifying chitooligosaccharide (COS) with cyanuric chloride (CC) for chrome-free leather manufacture. The synthesis of such biomass-based tanning agent was systematically optimized to obtain the target product with high grafting degree of 67% and weight-average molecular weight (Mw) of 1465 g/mol. The non-pickling tanning procedure using DTCS was investigated, and the interactions between DTCS and collagen fibers were studied. Our results showed that the hydrothermal stability of the tanned leather was significantly increased, i.e., the shrinkage temperature (Ts) exceeding 82.0°C, and the mechanical properties were improved. Moreover, the organoleptic properties of leather (e.g., fullness, softness and grain tightness) exhibited obvious improvement. This research not only offers a reliable approach for cleaner leather manufacturing while addressing the underlying ecological pressure, but also highlights the emerging use of biomass materials in the leather industry. Note de contenu : - MATERIALS AND METHODS : Materials - Synthesis of DTCS - Determination of grafting degree (GD) of DTCS - Characterization of DTCS - DTCS tanning trials - Leather properties analysis - RESULTS AND DISCUSSION : Optimization of DTCS synthesis condition - Characterization of DTCS - Optimizatin of DTCS tanning process - Leather morphology anlaysis - Thickening rate analysis - Physical and organoleptic properties analysis - Table 1 : Tanning process for DTCS - Table 2 : Tanning process for F-90 - Table 3 : The average molecular weight and molecular-weight distribution of COS and DTCS - Table IV : The optimum tanning process of DTCS DOI : https://doi.org/10.34314/jalca.v118i10.8230 En ligne : https://drive.google.com/file/d/1csGAWb8R-ZPLSmdInoTLfYTzOcUHK0KN/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=39940 [article]

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Effect of electrostatic interaction between collagen and enzymes on permeation of protease into the pelt during leather bating process / Yiwen Zhu in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CXVIII, N° 10 (10/2023)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CXVIII, N° 10 (10/2023) . - p. 428-438 Titre : Effect of electrostatic interaction between collagen and enzymes on permeation of protease into the pelt during leather bating process Type de document : texte imprimé Auteurs : Yiwen Zhu, Auteur ; Jinzhi Song, Auteur ; Xu Zhang, Auteur ; Mengchu Gao, Auteur ; Biyu Peng, Auteur ; Chunxiao Zhang, Auteur Année de publication : 2023 Article en page(s) : p. 428-438 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Caractérisation Confitage enzymatique Cuirs et peaux Electrostatique Peptidases Perméation Poids Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : The enzymatic delimed pelts bating process using proteases is critical to improving the overall performance of the leather. Bating effectiveness is determined not only by the properties but also by the permeation behavior of the proteases. Imperfect methods to control protease permeation often results in uneven distribution of enzyme proteins in the pelts, leading to excessive enzymolysis of the surface layer and inadequate opening-up of the inner layer. In this study, the relative size of proteases and delimed pelts were analyzed, the permeation behavior of fluorescein-labeled proteases in the pelt was observed using a confocal laser scanning microscope (CLSM), and the effect of electrostatic interaction between protease and collagen proteins on the permeation of protease into the pelt was investigated. The results showed that, after dehairing, liming and deliming operations, the enzyme can easily permeate into the pelts due to the formation of large cavities and interfibrillar gaps. The permeation of protease within the delimed pelt is significantly influenced by the affinity (electrostatic interactions) between the collagen and protease proteins. The isoelectric point (pI) of the protease protein, the collagen and the pH of the solution directly influence the electrostatic properties and interactions. When the enzyme and collagen are similarly charged (electrostatic repulsion), the enzyme can easily permeate into the pelts; when the enzyme and collagen are oppositely charged (electrostatic attraction), the permeation of the enzyme into the inner layer is difficult, resulting in the accumulation of protease on the grain and excessive hydrolysis of the grain layer. Therefore, the established permeation regulation mechanism of protease based on electrostatic interactions between enzyme and collagen could serve as an important basis for the selection of protease and the regulation of the enzymatic bating process. Note de contenu : - MATERIALS AND METHODS : Materials - Determination of protease particle size and delimed pelts pore diameter - Preparation and characteriztion of fluorescein-labeled proteases - RESULTS AND DISCUSSION : The particle size of protease in solution and pore diameter of delimed pelts - Determination of the pI of the delimed pelt - Characterization of the FITC-labeled proteases - UV-Vis spectroscopy characterization of FITC-labeled proteases - FLuorescence spectroscopy characterizations of FITR labeled proteases - pI and relative molecular weight of labeled proteases - Effect of proteins affinity on proteases permeation behavior in delimed pelts - Effect of pH on the surface of the pelts during enzymatic bating - Charge regulation mechanism of protease permeation in delimed pelts DOI : https://doi.org/10.34314/jalca.v118i10.8231 En ligne : https://drive.google.com/file/d/1xABUCLjci5t-d9y12Zp6saB4Vg83zurc/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=39941 [article]

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Use of long-chain synthetic phenolic antioxidants to produce chromium-tanned leather without risk of hexavalent chromium formation / Irene Compte in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CXVIII, N° 10 (10/2023)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CXVIII, N° 10 (10/2023) . - p. 439-449 Titre : Use of long-chain synthetic phenolic antioxidants to produce chromium-tanned leather without risk of hexavalent chromium formation Type de document : texte imprimé Auteurs : Irene Compte, Auteur ; Quim Torras, Auteur ; Francina Izquierdo, Auteur ; Rosa M. Cuadros, Auteur ; Anna Bacardit, Auteur Année de publication : 2023 Article en page(s) : p. 439-449 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Antioxydants Auto-oxydation Cuirs et peaux de moutons Essais accélérés (technologie) Lipides Phénols Tannage au chrome Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Chromium tanned leather is the widest form of leather tanning across the world, but it might involve a risk of hexavalent chromium formation, which is restricted in leather products above 3 mg/ kg. Among other conditions, certain processes might lead to the oxidation of natural fats or fatliquoring agents with unsaturated carbon-carbon bonds, thus generating free radical molecules that can contribute to the Cr(III) oxidation to Cr(VI). The autooxidation of unsaturated lipids is promoted by exposure to high temperatures and light, specifically UV radiation. Among other relevant manufacturing practices, the addition of synthetic phenolic antioxidants (SPAs) during the synthesis of fatliquoring agents or during leather manufacturing can be a relevant tool for preventing lipid auto-oxidation. The efficiency of the long-chain synthetic antioxidant 1135 (AO1135, CAS RN® 125643-61-0) has been assessed for Cr(VI) prevention. The performance of AO1135 has been tested in two different skin types (sheepskin, woolly sheepskin), with two different fatliquoring agents (unprotected and protected against oxidation). The protected fatliquoring agent was formulated with AO1135. Also, two commercial products that contain the AO1135 in its formulation have been applied to leathers. Upon completion of the post-tanning process, the leathers have undergone two different thermal ageing processes. AO1135 has been verified an effective SPA for Cr(VI) prevention and its application during the post-tanning process does not alter the visual aspect of the leathers. Otherwise, if the post-tanning recipe does not contain well-sourced raw materials or Cr(VI) prevention tools, unsaturated fatliquoring agents or natural fats present in the skins can be a cause for Cr(VI) formation. Note de contenu : - INTRODUCTION : Origins of Cr(VI) in leather-hexavalent chromium containing substances - Influence of the pH value - Oxidation of fatliquoring agents - Natural extracts as a way for reducing formed Cr(VI) - Synthetic phenolic antioxidants as a tool for preventing lipid auto-oxidation - Forcing lipid auto-oxidation in leather - Determining the efficiency of antioxidant 1135 to prevent Cr(VI) formation - Commercial products with synthetic phenolic antioxidant - EXPERIMENTAL : Design of the experiment - Samples - Chemicals and appartus - Methods - Determination of natural fat content in leather - RESULTS : Cr(VI) content in the tanned leathers - Dispersion of the Cr(VI) content depending on the different parts of the leather - DISCUSSION : Use of synthetic phenolic auxiliaries (AO1135) and its consequences on the Cr(VI) content - Zone of the leather and Cr(VI) distribution - Effect of different ageing treatments in Cr(VI) - Table 1 : Structure of the study - Table 2 : Conditions of sample exposure prior to Cr(VI) testing - Table 3 : Cr(VI) content according to ISO 17075-2:2017 of sheep-skins produced - Table 4 : Cr(VI) content according to ISO 17075-2:2017 of wooly sheep leathers produced - Table 5 : Average and % RSD of leathers with Cr(VI) detection DOI : https://doi.org/10.34314/jalca.v118i10.8232 En ligne : https://drive.google.com/file/d/1a3qDDoXd-GKDH-5gVHfu1cAh_Tje3ck8/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=39942 [article]

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