Resines acríliques modificades com a nous productes de readobament i/o adobament sense formol ni fenol
- Autores: Miquel Canudas Ventura
- Directores de la Tesis: Joan de Pablo Ribas (dir. tes.), Josep Maria Morera (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2020
- Idioma: español
- Materias:
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- Resumen
The leather manufacturing process consists of a sequence of complex chemical reactions and mechanical processes that allow turning skin, a putrefiable by-product of alimentary industry, into leather, a stable high-value-added product with good hydrothermal resistance.
During the last years, leather industry has evolved to an industry environmentally friendly thanks to the emergence of new chemicals and processes which have allowed the reduction of water and atmospheric emissions. One of these products has been conventional acrylic resins which are currently widely used as a retanning agents. However, they present a number of disadvantages in the final properties of the retanned leather. For this reason, in most cases, they are used together with different classic products constituted by formaldehyde, phenol, napthalene, etc. which have a certain degree of toxicity and possible carcinogenicity.
The still use of certain chemicals with toxic constituents that could not be substituted for renewable or less polluting products, the obtention of reaction byproducts difficult to recycle or reuse during the diferent stages of the process and, the low properties of the leather retanned with convencional acrylic resins, it can conclude that there is still a large margin for improvement to reduce the environmental impact of the leather industry.
In this doctoral thesis, modified acrylic resins known as polycarboxylates (PCEs) has been synthesized and studied as possible new environmentally friendly retanning agents instead of the conventional acrylic resins and classical products.
PCEs synthesis has been done in two phases: free radical polymerization followed by Fischer esterification. Thus, branched polymers formed by acrylic backbone chains esterified with polyalcoholic side chains have been obtained. The characterization of these products has been carried out at the structural level through infrared spectroscopy (IR) and at molecular weight level through size exclusion chromatography (SEC). Both methods have allowed the identificaction of products of the same chemical nature but with differences in the molecular weight of the backbone chains and/or the side chains.
The retanning tests have been carried out comparing their properties as retanning agents with a conventional linear acrylic resin of contrasted commercial use. The obtained leathers have been analyzed by physical and organoleptic assays. The results have shown that all PCE products render a high intensity of colour in the retanned leathers, one of the main drawbacks of the conventional acrylic resins. In addition, they have allowed to make a selection of the ideal PCE structure in relation to the application as a retanning agent. The validation of the obtained results has been done by scanning electron microscopy (SEM). To evaluate the environmental impact of the product, a biodegradability test has been performed. It has allowed to determine that PCE products have a higher degree of biodegradability compared to conventional acrylic resins. Consequently, as they are products with a high degree of biodegradability that don’t require the complementary use of classical toxic products, they can be considered as highly environmentally friendly products which can help to reduce the environmental impact of the leather industry life cycle.
This project concludes that, in comparison to the conventional acrylic resins, PCEs are a real alternative of enhanced retanning agents more respectful with the environment.
