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

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

Libro de calidad para la producción de piel y cuero libre de Cromo(VI)

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Quality handbook for the production of chromium(VI)-free leather

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Prevention of chromium(VI) formation by improving the tannery processes

This work has been funded by the European Commission through the Chrom6less Project (CRAFT -1999-71638). The objectives of the project were: - Establishment of the analytical methodology which provided reproducible results that may be free of interferences. - Identification of the factors that facilitated or impeded the transformation of Cr(III) to Cr(VI). - Establishment of the best conditions that allowed the production of chromium(VI) free leather, even during the life of the product, in contact with environmental agents such as light or heat. The following partners participated in the project: Inpelsa, Dercosa, Proquip, Igualada Leather Technology School, CID-CSIC and Miguel Hernandez University, from Spain, Gmelich, Knoll Sitzleder, and Lederinstitut Gerberschule Reutlingen from Germany, and Conceria Il Cigno, Calzaturificio Accademia and Stazione Experimentale from Italy. Hundreds of samples have been analysed during the project. In order to study the influence of several factors in chromium (VI) formation, a lot of skins/hides have been produced. Several leather articles (hides for clothing, footwear, upholstery, leather goods and furniture upholstery and skins for suede and double face)) have been manufactured free from Cr (VI). The main results obtained were: - The new analytical method CEN/TS 14495 has been validated. - Protective measures for the prevention of chromium (VI) formation have been identified. - New formulations for several hides/skins have been developed. - A handbook for the production of chromium (VI)-free leather has been published. The main conclusions of the project were: - The Chrom6less Project has shown that most of the skins/leathers did not contain hexavalent chromium. - It is now possible to confidently determine the Cr(VI) content in all kinds of leather regardless of their colour. - The application of protective measures developed in the Project allows leather to resist the effect of ageing without the formation of Cr(VI)

Determinación de TCMTB y otros fungicidas en piel

La norma ISO 13365:2011 desarrolla un método analítico para la determinación del contenido de los agentes conservantes 2-(tiocianometiltio)-benzotiazol (TCMTB), 4-cloro-3-metilfenol (PCMC), 2-fenilfenol (OPP) y 2-octil-3(2H)-isotiazolona (OIT) en cuero por cromatografía líquida. La determinación simultanea de los fungicidas TCMTB, PCMC, OPP, OIT, y también de 2-mercaptobenzothiazol (MBT) y 3-yodo-2-propinil-butilo (IPBC) en muestras de piel se llevó a cabo mediante cromatografía líquida (HPLC) con detector ultravioleta de fotodiodos (PDA). La preparación de la muestra y el proceso de extracción se realizaron siguiendo la norma ISO 13365. La fase móvil consistió en agua con un 0.1% de ácido fórmico (A) y acetonitrilo con un 0.1% de ácido fórmico (B). En la detección cromatográfica se introdujo un pequeño cambio en relación con la norma. Se utilizó un detector de fotodiodos en lugar de un detector de longitud de onda fija para mejorar la fiabilidad de las identificaciones y la sensibilidad de la cuantificación. Se ha comprobado que el 2,4,6-triclorofenol (TCP) y el pentaclorofenol (PCP) no interfieren en la determinación. Las fortificaciones de 30 y 300 mg/kg en cuero produjeron unas recuperaciones medias de TCMTB del 94% y 99%, respectivamente. Las recuperaciones de los otros fungicidas fueron similares. Los fungicidas investigados se determinaron en 40 muestras de cueros del mercado. En el 90% de las muestras se encontraron residuos de TCMTB. En resumen, la nueva norma ISO 13365:2011 proporciona un método rápido y fiable, no sólo para la determinación de las cuatro moléculas incluidas en el ámbito de aplicación de la norma, sino también para otros fungicidas como el IPBC y el MBTPostprint (published version

Prevention of chromium(VI) formation by improving the tannery processes

This work has been funded by the European Commission through the Chrom6less Project (CRAFT -1999-71638). The objectives of the project were: - Establishment of the analytical methodology which provided reproducible results that may be free of interferences. - Identification of the factors that facilitated or impeded the transformation of Cr(III) to Cr(VI). - Establishment of the best conditions that allowed the production of chromium(VI) free leather, even during the life of the product, in contact with environmental agents such as light or heat. The following partners participated in the project: Inpelsa, Dercosa, Proquip, Igualada Leather Technology School, CID-CSIC and Miguel Hernandez University, from Spain, Gmelich, Knoll Sitzleder, and Lederinstitut Gerberschule Reutlingen from Germany, and Conceria Il Cigno, Calzaturificio Accademia and Stazione Experimentale from Italy. Hundreds of samples have been analysed during the project. In order to study the influence of several factors in chromium (VI) formation, a lot of skins/hides have been produced. Several leather articles (hides for clothing, footwear, upholstery, leather goods and furniture upholstery and skins for suede and double face)) have been manufactured free from Cr (VI). The main results obtained were: - The new analytical method CEN/TS 14495 has been validated. - Protective measures for the prevention of chromium (VI) formation have been identified. - New formulations for several hides/skins have been developed. - A handbook for the production of chromium (VI)-free leather has been published. The main conclusions of the project were: - The Chrom6less Project has shown that most of the skins/leathers did not contain hexavalent chromium. - It is now possible to confidently determine the Cr(VI) content in all kinds of leather regardless of their colour. - The application of protective measures developed in the Project allows leather to resist the effect of ageing without the formation of Cr(VI).Postprint (published version

Determinación de TCMTB y otros fungicidas en piel

La norma ISO 13365:2011 desarrolla un método analítico para la determinación del contenido de los agentes conservantes 2-(tiocianometiltio)-benzotiazol (TCMTB), 4-cloro-3-metilfenol (PCMC), 2-fenilfenol (OPP) y 2-octil-3(2H)-isotiazolona (OIT) en cuero por cromatografía líquida. La determinación simultanea de los fungicidas TCMTB, PCMC, OPP, OIT, y también de 2-mercaptobenzothiazol (MBT) y 3-yodo-2-propinil-butilo (IPBC) en muestras de piel se llevó a cabo mediante cromatografía líquida (HPLC) con detector ultravioleta de fotodiodos (PDA). La preparación de la muestra y el proceso de extracción se realizaron siguiendo la norma ISO 13365. La fase móvil consistió en agua con un 0.1% de ácido fórmico (A) y acetonitrilo con un 0.1% de ácido fórmico (B). En la detección cromatográfica se introdujo un pequeño cambio en relación con la norma. Se utilizó un detector de fotodiodos en lugar de un detector de longitud de onda fija para mejorar la fiabilidad de las identificaciones y la sensibilidad de la cuantificación. Se ha comprobado que el 2,4,6-triclorofenol (TCP) y el pentaclorofenol (PCP) no interfieren en la determinación. Las fortificaciones de 30 y 300 mg/kg en cuero produjeron unas recuperaciones medias de TCMTB del 94% y 99%, respectivamente. Las recuperaciones de los otros fungicidas fueron similares. Los fungicidas investigados se determinaron en 40 muestras de cueros del mercado. En el 90% de las muestras se encontraron residuos de TCMTB. En resumen, la nueva norma ISO 13365:2011 proporciona un método rápido y fiable, no sólo para la determinación de las cuatro moléculas incluidas en el ámbito de aplicación de la norma, sino también para otros fungicidas como el IPBC y el MB