Influència dels processos d’engreix en la formació de Cr(VI) de la pell

Una de les problemàtiques més importants en el sector del curtits és la presència de crom (VI) en el producte acabat. Això és degut a que en el 90% de la producció de curtits s’utilitzen les sals de crom (III) com a agent curtient. Un cop la pell està acabada, diferents factors poden fer que aquest Cr(III) s’oxidi a Cr(VI) al llarg de la seva vida útil. Això pot suposar un greu problema ja que es classifica el crom (VI) com un producte altament tòxic, de caràcter cancerigen. El contingut de Cr(VI) a la pell és un dels paràmetres ecotoxicològics present en les diferents normes o ecoetiquetes que existeixen. El present treball està inclòs dins un projecte europeu amb participants de 3 països diferents (Espanya, Itàlia i Alemanya) en el que es pretenen modificar alguns passos dels processos de teneria per tal de prevenir la formació de Cr(VI). L’etapa que estudia el present projecte de final de carrera és la d’engreix, que és l’aplicació de productes engreixants a la pell amb la finalitat d’obtenir un producte de tacte i estructura molt més suau i tova. En una primera part del treball, es defineix el procés d’adoberia de la pell, fent una explicació molt més detallada de l’etapa d’engreix. En la part experimental es veu com influeixen els engreixos en la formació de crom (VI), aplicant la fórmula triada i posteriorment fent la determinació de crom amb el mètode oficial (IUC18). Es comparen diferents característiques dels olis i greixos i es veu com afecten aquestes propietats en la formació de crom (VI), ja que aquests actuen de distinta manera depenent de diferents paràmetres; l’índex de iode, l’origen, la quantitat aplicada, la seva naturalesa,... Els estudis desenvolupats han confirmat que hi ha uns determinats olis que afavoreixen clarament l’aparició de crom en l’estat màxim d’oxidació, com són, sobretot, els olis amb major presència de dobles enllaços. Aquests engreixos presenten un alt grau d’insaturació que els fa fortament oxidants. Altres característiques com una major aplicació d’engreix o un procés sense eliminació prèvia del greix natural de la pell, abans de realitzar la curtició afavoreixen també la formació de crom (VI) en el producte acabat. En una segona etapa, es verifica que l’aplicació de productes amb característiques antioxidants (extracte de tara, vitamina E, antioxidants fenòlics i amínics, vitamina C) al procés de curtició poden evitar que el crom (III) present a la pell es transformi en l’estat del metall no desitjat

Fungicides alternatius per a la indústria de la pell : comparació amb productes convencionals

This thesis is focused on the search of alternatives to fungicides conventionally used in the tanning industry. These chemicals must be effective against a large number of fungi less toxic, more environmentally friendly and economically attractive. The main objective is to evaluate the fungicidal capacity of selected alternative compounds (Directive 98/8/CE); diiodometil p-tolylsulfone (DIMPTS), 3-Iodo-2-propynyl butylcarbamate (IPBC), thiabendazole (TBZ) and dodicine clorhydrate (TEGO) versus different types of fungi. The strains used belong to the most common species in tanneries: Aspergillus brasilensis, Trichoderma harzianum, Alternaria alternata i Penicillium funiculosum. In addition, different fungi from real pollution tannery have been isolated from the industry; these are species more resistant to common antifungal chemicals. The antifungal capacity has been compared with selected fungicides normally used in tanneries, such as 2-(thiocianometilthio)-1,3-benzothiazole (TCMTB) and the mixture of phenolic compounds, p-chloro-m-cresol (PCMC) and o-phenylphenol (OPP). First, the Minnimum Inhibition Concentration (MIC) of molecules has been determine against the selected fungi. Subsequently, the effectiveness of different offers of chemicals has been compared using wet blue leather. To complete the tests, selected fungicides have been applied in three different processes: a chrome tanning process, a preservative pickling process and a fatliquoring process of hides tanned with vegetable extracts. Further studies consisted of a microbiological control of samples inoculated with fungi common in tannery, determination of the minimum effective amount of chemical and determination of the fungicide content on the different layers of the hide. The evaluation of the toxicity of process wastewaters associated with their application and the economic viability of the proposed alternatives complemented the studies. The higher antifungal capacity of two of the four fungicides proposed, DIMPTS and IPBC, employed in different processes confirms that are good candidates to be used in the leather sector. Hides obtained using alternative fungicides showed good characteristics, and, from the environmental impact point of view, toxicity from wastewaters was lower for the alternative chemicals against those commonly used.Aquesta tesi es basa en la recerca d’alternatives als fungicides convencionalment utilitzats en la indústria adobera. Aquests productes han de ser eficaços enfront un alt nombre de fongs, menys tòxics, més acceptables mediambientalment i atractius econòmicament. El principal objectiu és avaluar la capacitat antifúngica dels compostos seleccionats (registrats en la Directiva 98/8/CE); diiodometil-p-tolilsulfona, DIMPTS, 3-iodo-2-propinil-Nbutilcarbamat, IPBC, tiabendazol, TBZ, i la sal sòdica de dodecil-di(aminoetil)-glicina, TEGO, davant diferents tipus de fongs. Les soques utilitzades formen part de les espècies més comuns en les adoberies: Aspergillus brasilensis, Trichoderma harzianum, Alternaria alternata i Penicillium funiculosum. A part, s’han aïllat tres fongs diferents d’indústries adoberes per poder treballar amb contaminacions reals, espècies més resistents als productes antifúngics habituals. La capacitat antifúngica dels compostos seleccionats s’ha comparat amb els fungicides usats normalment en les adoberies: el 2-(tiocianometiltio)-1,3-benzotiazol, TCMTB, i una barreja de compostos fenòlics (p-cloro-m-cresol, PCMC, i o-fenilfenol, OPP). Primer s’ha determinat la Concentració Mínima d’Inhibició (CMI) de les molècules seleccionades davant els fongs descrits. Posteriorment, utilitzant pell wet blue per l’estudi, s’ha comparat l’eficàcia dels productes amb diferents ofertes de cadascun d’ells. Per completar els assajos, s’han aplicat els fungicides escollits en tres processos diferents: un adobament al crom, un píquel de conservació i un greixatge de pell adobada amb extractes vegetals. Sobre la pell obtinguda en cada procés s’han realitzat diverses proves de control de creixement de fongs per avaluar l’eficàcia dels productes, la determinació de la mínima quantitat de producte efectiva i la determinació del fungicida que resta en les diferents capes de la pell. L’avaluació de la toxicitat dels productes associada amb la seva aplicació i la viabilitat econòmica de les alternatives proposades complementen els estudis. L'elevada capacitat antifúngica demostrada utilitzant dos dels quatre fungicides proposats, el DIMPTS i el IPBC confirmen que són bons candidats per utilitzar-se com a fungicides alternatius en la indústria de la pell. Les pells obtingudes utilitzant aquests dos productes presenten bones característiques i l’impacte mediambiental és menor ja que la toxicitat de les aigües residuals obtingudes és més baixa que la toxicitat causada per l’aplicació dels productes convencionals

Dyestuffs and formaldehyde content in split leather treated with formaldehyde resins

Formaldehyde resins are present in textile, leather and wood industries. Due to the harmful character of formaldehyde, different alternatives have been found to exclude or reduce its content on processed goods. However, the effect of dyestuffs on the formaldehyde content of goods containing formaldehyde-synthesized resins has not been studied up to date. The aim of this work is to check if the presence of free amino groups in the structure of dyestuffs exerts an influence on the formaldehyde content on leathers treated with formaldehyde-synthesized resins. Six dyes, belonging to three different families (acid dyes, direct dyes and basic dyes), have been taken as examples to evaluate how their structures affect the reaction with formaldehyde present in leather. The variation of the formaldehyde content in dyed leathers with respect to control samples (treated with resin only) and its evolution with time have been also considered. It has been found that the ability of dyes in reducing the formaldehyde content in leather depends on the amount of amino groups amenable to reaction with formaldehyde. Those amino groups that in their vicinity have other functionalities, with which to form relatively stable structures, have a reduced reactivity with formaldehyde. The reduction ability of dyes also depends on the formaldehyde content in leather. The lower the formaldehyde content is in the leather, the higher this reduction ability. Acid Black 234 dye caused a formaldehyde content reduction of approximately 84% in leathers treated with melamine-formaldehyde resin of low formaldehyde content in the analysis carried out after 90 days of leather processing whereas the reduction was approximately 20% when the resin was of high formaldehyde content. The highest reduction ability of basic dyes corresponded to the dye that has the greatest amount of amino residues amenable to reaction with formaldehyde (Basic Orange 2). Basic Orange 2 dye exhibited higher reduction ability (90% of reduction in leathers treated with resin of high formaldehyde content after 90 days of leather processing) than the Acid Black 234 dye (approximately 20%), both containing similar amount of free amino residues. Thin layer chromatography analysis revealed that the Basic Orange 2 dye is mainly a single major component, while the Acid Black dye 234 is a mixture of components that can have a reduced reactivity with formaldehyde. Further experiments are required to investigate if the surface leather dyeing (Basic Orange 2 dye) have a higher influence on formaldehyde content reduction than the through-dyeing (Acid Black 234 dye).Peer ReviewedPostprint (published version

Reduction of the formaldehyde content in leathers treated with formaldehyde resins by means of plant polyphenols

Formaldehyde has applications in many industrial processes, including synthesis of resins and syntans to be used in the retanning process of leather. When resins are employed, they can hydrolyse, releasing formaldehyde. Due to the carcinogenicity of formaldehyde, its presence in leather should be avoided or kept below allowable limits. The aim of this study is to determine the effect of polyphenols contained in vegetable compounds (mimosa, quebracho and tara) in the reduction of the formaldehyde content in leathers treated with resins synthesized with formaldehyde (melamine-formaldehyde and dicyandiamide-formaldehyde). The formaldehyde content in leathers treated only with resin increases with time while the formaldehyde content in leathers treated additionally with vegetable compounds is reduced. The lower the formaldehyde content in the leather, the higher the ability of vegetable compounds to reduce such content. Mimosa shows the strongest ability to reduce the formaldehyde content, and this capacity increases with ageing. The addition of 4% (on shaved wet-blue weight) of mimosa gives rise to an 85% reduction in the formaldehyde content 140 days after leather processing of split hides treated with a formaldehyde resin of low formaldehyde content. However, this reduction is 68% in splits hides treated with a resin of high formaldehyde content. This is of great importance in baby’s leather articles, in which the formaldehyde content is low; therefore, the addition of a small amount (3%) of vegetable compounds (especially mimosa) guarantees that the formaldehyde content is below the allowed limits (16 mg/kg in the most restrictive regulation). Reducing the formaldehyde content using the polyphenols contained in vegetable compounds constitutes a good alternative not only in the leather sector but also in other industrial sectors (wood, textile, etc.) that use formaldehyde resins.Peer ReviewedPostprint (published version

Formaldehyde scavengers for cleaner production: A case study focused on the leather industry

Due to its carcinogenic character, the presence of formaldehyde in leather continues to be a subject of great concern. By using formaldehyde scavengers, it is possible to reduce the formaldehyde content in leather. In this work, the potential ability of three different compounds (ethylene urea, pyrogallol and gallic acid) to reduce the formaldehyde content in splits leathers treated with formaldehyde resins (melamine-formaldehyde and dicyandiamide-formaldehyde) is assessed. This capacity is compared with that of a fourth scavenger (hydroxylamine sulphate) already used in tanneries. The evolution of the formaldehyde content with time is also considered, as well as the potential coadjuvant effect of other compounds such as mimosa extract and an acid dye (Acid Black 234). Hydroxylamine sulphate initially showed the highest ability to reduce formaldehyde content. However, after a certain time, this ability proved to be inferior to the ability of other compounds due to the reversibility of the reaction between hydroxylamine and formaldehyde. Pyrogallol showed a higher ability than gallic acid when used in the final wash of leather processing. However, the treatment with pyrogallol results in a darkening of the leather; this darkening limits its use. Gallic acid may be a good alternative to formic acid as the final fixing agent in leather processing when the presence of formaldehyde in leathers is suspected. The use of gallic acid in the final wash or as a fixing agent fulfils the formaldehyde content limit (65–75 mg/kg) of the major brands in leather goods in direct contact with the skin. The addition of 2% of gallic acid in the final wash of leather processing resulted in formaldehyde content reductions that varied from 65% to 85%. However, further experiments are required to assess the influence of gallic acid on the fastness properties and the coloration acquired by the treated leathers. The joint effect of gallic acid in the final wash or as a fixing agent and mimosa extract as a retanning agent in formaldehyde content reduction is even enhanced by subsequently using a dye with amino groups in its chemical structure. Reducing the formaldehyde content by using scavengers can contribute to the achievement of a cleaner production in those sectors (leather, textile, wood) that use formaldehyde resins

Influència dels processos d’engreix en la formació de Cr(VI) de la pell

Una de les problemàtiques més importants en el sector del curtits és la presència de crom (VI) en el producte acabat. Això és degut a que en el 90% de la producció de curtits s’utilitzen les sals de crom (III) com a agent curtient. Un cop la pell està acabada, diferents factors poden fer que aquest Cr(III) s’oxidi a Cr(VI) al llarg de la seva vida útil. Això pot suposar un greu problema ja que es classifica el crom (VI) com un producte altament tòxic, de caràcter cancerigen. El contingut de Cr(VI) a la pell és un dels paràmetres ecotoxicològics present en les diferents normes o ecoetiquetes que existeixen. El present treball està inclòs dins un projecte europeu amb participants de 3 països diferents (Espanya, Itàlia i Alemanya) en el que es pretenen modificar alguns passos dels processos de teneria per tal de prevenir la formació de Cr(VI). L’etapa que estudia el present projecte de final de carrera és la d’engreix, que és l’aplicació de productes engreixants a la pell amb la finalitat d’obtenir un producte de tacte i estructura molt més suau i tova. En una primera part del treball, es defineix el procés d’adoberia de la pell, fent una explicació molt més detallada de l’etapa d’engreix. En la part experimental es veu com influeixen els engreixos en la formació de crom (VI), aplicant la fórmula triada i posteriorment fent la determinació de crom amb el mètode oficial (IUC18). Es comparen diferents característiques dels olis i greixos i es veu com afecten aquestes propietats en la formació de crom (VI), ja que aquests actuen de distinta manera depenent de diferents paràmetres; l’índex de iode, l’origen, la quantitat aplicada, la seva naturalesa,... Els estudis desenvolupats han confirmat que hi ha uns determinats olis que afavoreixen clarament l’aparició de crom en l’estat màxim d’oxidació, com són, sobretot, els olis amb major presència de dobles enllaços. Aquests engreixos presenten un alt grau d’insaturació que els fa fortament oxidants. Altres característiques com una major aplicació d’engreix o un procés sense eliminació prèvia del greix natural de la pell, abans de realitzar la curtició afavoreixen també la formació de crom (VI) en el producte acabat. En una segona etapa, es verifica que l’aplicació de productes amb característiques antioxidants (extracte de tara, vitamina E, antioxidants fenòlics i amínics, vitamina C) al procés de curtició poden evitar que el crom (III) present a la pell es transformi en l’estat del metall no desitjat

Dyestuffs and formaldehyde content in split leather treated with formaldehyde resins

Formaldehyde resins are present in textile, leather and wood industries. Due to the harmful character of formaldehyde, different alternatives have been found to exclude or reduce its content on processed goods. However, the effect of dyestuffs on the formaldehyde content of goods containing formaldehyde-synthesized resins has not been studied up to date. The aim of this work is to check if the presence of free amino groups in the structure of dyestuffs exerts an influence on the formaldehyde content on leathers treated with formaldehyde-synthesized resins. Six dyes, belonging to three different families (acid dyes, direct dyes and basic dyes), have been taken as examples to evaluate how their structures affect the reaction with formaldehyde present in leather. The variation of the formaldehyde content in dyed leathers with respect to control samples (treated with resin only) and its evolution with time have been also considered. It has been found that the ability of dyes in reducing the formaldehyde content in leather depends on the amount of amino groups amenable to reaction with formaldehyde. Those amino groups that in their vicinity have other functionalities, with which to form relatively stable structures, have a reduced reactivity with formaldehyde. The reduction ability of dyes also depends on the formaldehyde content in leather. The lower the formaldehyde content is in the leather, the higher this reduction ability. Acid Black 234 dye caused a formaldehyde content reduction of approximately 84% in leathers treated with melamine-formaldehyde resin of low formaldehyde content in the analysis carried out after 90 days of leather processing whereas the reduction was approximately 20% when the resin was of high formaldehyde content. The highest reduction ability of basic dyes corresponded to the dye that has the greatest amount of amino residues amenable to reaction with formaldehyde (Basic Orange 2). Basic Orange 2 dye exhibited higher reduction ability (90% of reduction in leathers treated with resin of high formaldehyde content after 90 days of leather processing) than the Acid Black 234 dye (approximately 20%), both containing similar amount of free amino residues. Thin layer chromatography analysis revealed that the Basic Orange 2 dye is mainly a single major component, while the Acid Black dye 234 is a mixture of components that can have a reduced reactivity with formaldehyde. Further experiments are required to investigate if the surface leather dyeing (Basic Orange 2 dye) have a higher influence on formaldehyde content reduction than the through-dyeing (Acid Black 234 dye).Peer Reviewe

Determination of formaldehyde content in leather: Standard EN ISO 17226, revision and possible improvements

The retanning process is the main application of formaldehyde in the tanning industry since formaldehyde participates in two groups of synthetic organic tanning agents: syntans and resins. Resins can be hydrolysed with the result that formaldehyde is released. Thus, formaldehyde in leather can be free or from hydrolysis of resins. Due to the carcinogenic character of formaldehyde, its presence in leather should be avoided or should be below allowable limits. The EN ISO 17226 Standard is the Official Standard for the determination of formaldehyde content in leather, which, in the authors’ opinion, presents certain ambiguities in the wording of some operations included in their analysis methods and, some of these operations, are susceptible of improvement. Therefore, a revision of the EN ISO 17226 Standard (Parts 1 and) 2 is carried out in this work and, in particular, of the extraction phase of formaldehyde present in leather (possible use of alternative surfactant and shaking method); reaction time between the extracted formaldehyde with the dinitrophenylhydrazine solution (Part 1 of the Standard) and stability of the acetylacetone solution (Part 2 of the Standard).Peer ReviewedPostprint (published version

Determination of formaldehyde content in leather: Standard EN ISO 17226, revision and possible improvements

The retanning process is the main application of formaldehyde in the tanning industry since formaldehyde participates in two groups of synthetic organic tanning agents: syntans and resins. Resins can be hydrolysed with the result that formaldehyde is released. Thus, formaldehyde in leather can be free or from hydrolysis of resins. Due to the carcinogenic character of formaldehyde, its presence in leather should be avoided or should be below allowable limits. The EN ISO 17226 Standard is the Official Standard for the determination of formaldehyde content in leather, which, in the authors’ opinion, presents certain ambiguities in the wording of some operations included in their analysis methods and, some of these operations, are susceptible of improvement. Therefore, a revision of the EN ISO 17226 Standard (Parts 1 and) 2 is carried out in this work and, in particular, of the extraction phase of formaldehyde present in leather (possible use of alternative surfactant and shaking method); reaction time between the extracted formaldehyde with the dinitrophenylhydrazine solution (Part 1 of the Standard) and stability of the acetylacetone solution (Part 2 of the Standard).Peer Reviewe

Determination of formaldehyde content in leather: Standard EN ISO 17226, revision and possible improvements

The retanning process is the main application of formaldehyde in the tanning industry since formaldehyde participates in two groups of synthetic organic tanning agents: syntans and resins. Resins can be hydrolysed with the result that formaldehyde is released. Thus, formaldehyde in leather can be free or from hydrolysis of resins. Due to the carcinogenic character of formaldehyde, its presence in leather should be avoided or should be below allowable limits. The EN ISO 17226 Standard is the Official Standard for the determination of formaldehyde content in leather, which, in the authors’ opinion, presents certain ambiguities in the wording of some operations included in their analysis methods and, some of these operations, are susceptible of improvement. Therefore, a revision of the EN ISO 17226 Standard (Parts 1 and) 2 is carried out in this work and, in particular, of the extraction phase of formaldehyde present in leather (possible use of alternative surfactant and shaking method); reaction time between the extracted formaldehyde with the dinitrophenylhydrazine solution (Part 1 of the Standard) and stability of the acetylacetone solution (Part 2 of the Standard).Peer Reviewe