[ca] La utilització dels ultrasons en sistemes d'adobament vegetal presenta avantatges respecte els sistemes més consolidats en la indústria en l'actualitat: adobaments vegetals dinàmics on s'utilitzen els bombos com a reactor, i adobaments vegetals estàtics o s'utilitzen les tines com a reactor. Els adobaments vegetals dinàmics s'utilitzen en la majoria d'articles adobats al vegetal i presenten un temps de procés reduït(1 a 4 dies) basat en la ràpida difusió del taní degut a l'elevat efecte mecànic que es produeix a l'interior dels bombos. En contrapartida aquest efecte és el causant de danys irreversibles en la dermis de la pell que poden reduir la qualitat del producte considerablement. Els adobaments vegetals estàtics s'utilitzen principalment en aquells articles (soles i similars) on l'oferta de taní per adobar la pell és tan elevada que ni el correcte control dels principals paràmetres que intervenen en l'adobament eviten danys molt greus en la dermis de la pell. En aquest casos s'opta per sistemes estàtics d'adobament on la pell es submergeix en tines a diferent concentració de taní per dur a terme l'adobament. En aquests sistemes l'efecte mecànic és pràcticament nul, però el temps de procés és llarg (7 a 90 dies) fet que redueix la productivitat i obliga a gestionar un estoc més elevat. L'objectiu principal d'aquesta tesi és dissenyar un sistema d'adobament vegetal per ultrasons a nivell industrial que aprofiti els avantatges dels sistemes que s'utilitzen actualment i n'eviti les seves problemàtiques a fi i efecte d'aconseguir un producte final amb una major qualitat i amb un grau d'optimització del procés que el permeti ser viable industrialment. El sistema preveu utilitzar la potència ultrasònica per disminuir la grandària molecular de les micel·les de taní i així aconseguir una ràpida difusió a través de la pell, sense necessitat d'aplicar efecte mecànic a bombo, i accelerant molt el procés respecte a un sistema estàtic.

[en] The use of ultrasound in the vegetable tanning processes, show nowadays, some advantages compared with the standard industrial systems like: dynamic vegetable tanning processes where drums are used as a reactor and static vegetable tanning processes where pits are used as a reactor. The dynamic vegetable tanning process is the most common method to produce full vegetable tanned articles. The production time is quite short (between 1 to 4 days), based on the quick diffusion of the vegetable agents due to mechanical effect produced inside the drums. In contrast, the mentioned mechanical effect can produce irreversible damages in the grain side that decreases the quality of the final product. The static vegetable tanning processes are mainly used in those kind of articles (sole Leather and similar) where the amount of tanning agents to make the product is so high that even the right control of the main parameters involved in the process can't avoid heavy damages in the grain side. With this kind of articles, the skins are immersed in pits with different tannin offers. In this case, the mechanical effect is none, which makes the process long in time (between 7 to 90 days). This point reduces the productivity and forces to administrate a bigger leather stock. The main objective of this PhD is to design a vegetable tanning process assisted by ultrasound, which could take advantage from the standard processes used nowadays and could solve the problems related with each one. This could bring us to a final product with a better quality and a possible process optimization that could make it industrially viable. The system uses the ultrasound waves to reduce the molecular size of the tanning agent's micelles, producing a quick diffusion through the skin without the use of any mechanical effect, and speeding up the process compared to the static system. In order to achieve the exposed objectives the thesis has been structured in 3 parts: Initial study: Pilot study to determine the performance of the parameters involved in the ultrasonic tannage and selection of the ideal conditions in order to prepare the next steps of the process. Study in the penetration stage: Based on the results obtained in the pilot study, an assessment in the penetration stage is proposed. In this phase, the parameters that take part in the tanning agent's diffusion all over the fiber structure of the skin will be studied. Study in the fixation stage: Based on the results obtained in the penetration stage the study in the fixation stage will be proposed. In this phase, the parameters performing in the fixation of the tanning agents will be studied once it has penetrated completely, in order to optimize the fixation and complete the tanning process. In order to evaluate the trials done in the experimental stages, the tanning degree will be used as an indicator. This parameter links the percentage of fixed tannin with the percentage of hide substance, enabling to quantify the absorption. Due to the difficulty to obtain this parameter and the amount of trials done to make this thesis, it will be worth to use new methodologies to obtain this value for future studies. After assessing the 3 stages, an ultrasonic working process alternative to the existing systems will be proposed.