The Future of polyurethane applications in leather: are NIPUs suitable candidates?
Leather is a durable material obtained from tanning or chemical treatment of animal skin, it is a by-product of the slaughter of the meat industry with great variety of applications. But it is far-away from green chemistry principles, it is a very unsustainable activity which consumes large amount o...
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| Tipo de recurso: | tesis de maestría |
| Fecha de publicación: | 2024 |
| País: | España |
| Institución: | Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya) |
| Repositorio: | Recercat. Dipósit de la Recerca de Catalunya |
| OAI Identifier: | oai:recercat.cat:10459.1/466522 |
| Acceso en línea: | https://hdl.handle.net/10459.1/466522 |
| Access Level: | acceso abierto |
| Palabra clave: | Polyurethane Leather finishing NIPU Natural Oil Polyol (NOP) PUs isocyanate-free |
| Sumario: | Leather is a durable material obtained from tanning or chemical treatment of animal skin, it is a by-product of the slaughter of the meat industry with great variety of applications. But it is far-away from green chemistry principles, it is a very unsustainable activity which consumes large amount of resources and generates a great number of pollutants. For this reason tanning industry is continuously focused in developing new greener production strategies. The production of leather goods is done in different processes by stages: first operations involves from raw hides to wet blue/white (from freezing to tanning), followed by the process from wet blue/white to crust leather (from sammyng to staking) and last process, the finishing, covers from crust leather to cut pieces (from buffing to cutting). Polyurethanes (PUs) are the most common polymers used in leather in the finish process as coating layer. PUs are based on the reaction of isocyanate (NCO) with polyol/amine groups followed by dispersion in solvent. The key of the polyurethanes is the high reactivity of the isocyanate group due to its resonant structure that promotes the reactivity towards nucleophilic attack and allows its versatility. But Isocyanates are in the spotlight both for the synthesis from phosgenation of amines and for the toxicity emanating from isocyanate monomers. On the other side, there is an increasing availability of polyols and amines of natural origin that reduce the pollutant load of polyurethanes and “promotes” its sustainability, beside the use of aqueous dispersion which eliminates the VOCs emission during finishing process. This work proposes more eco friendly and non-toxic alternatives to conventional PUs, using bio-products and/or novel route named NIPU (non-isocyanate PUs) to diminish the use of petroleum-based materials and solvents. To increase the sustainability of polyurethanes, research is being carried out to eliminate the isocyanate component from the synthesis of PUs, i.e. NIPUs. From the proposed routes to generate PUs isocyanate-free: poly-condensation, rearangement, ring opening polymerisation and poly-addition,[1] , the last one seems to be the most encouraging, based on the reaction of polycarbonates and polyamine. This option does not produce by products, it is solvent-free and the raw material used are non-toxic. Polyol are made from crude oil that is a limited resource, many investigations and efforts are done in searching raw material alternative sustainable, either by using agricultural by-products or materials that can be easily regenerated, as vegetal oils, forming the family of bio-polyols. NIPU (Non-isocyanate PU) combine biological and chemical carbon dioxide fixation. They are obtained by reacting polycyclic carbonate oligomers and aliphatic polyamines containing primary amino groups. As intermediate for the synthesis of cyclic carbonates renewable materials as vegetable oils, terpenes and lignin are, later they are cured with group amino. Once the NIPU is synthesized it is dispersed in aqueous media to obtain water-borne PUD |
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