Process to obtain tannin vegetable extracts to be used as tanning extracts for hides and skins

Kurzfassung

A Catalan technical centre based in Spain has developed a process providing the solubilisation by chemical reaction under pressure and temperature conditions and further purification and concentration of the tannins. Vegetable tannins to be used in leather tanning can be obtained from a wide range of vegetable sources, most of them being available as natural local sources or easily collected from agricultural harvest. Partners such as tanneries are sought for technical cooperation agreements.

Details

Most of the vegetable extracts used in the tanning industry come from South America and South Africa, and their obtaining have a considerable impact on these indigenous species.

The purpose of the technology is to avoid or minimise the deforestation of some species of trees, such as quebracho, mimose, chestnut, mirabolan, valonea and tara, commonly used in leather tanning. The study proposes to replace these vegetable tanning agents by a natural local source.

The process starts with the characterisation of the possible natural local sources of tannins (forest waste, fruits, and forestry species) to determine the tannin content.

The technology is based on the tannin extraction of the natural source in a special reactor with the optimal conditions of temperature, pressure and time process.
The tannin solution can be concentrated by evaporation and atomisation to obtain a powder product, or it can be concentrated by membrane technology to obtain a liquid tanning product.

Innovative Aspects:
The innovative aspects in relation to existing products or processes is the use of renewable and local sources, thus the deforestation is minimised.
Specifically, the company has the patent ES 2 197 821 B1 to obtain a vegetable tannin extract from grape waste (pomace) useful for tanning hides and skins. This technology can be adjusted to other possible local natural sources. In this way, this process is environmental friendly by minimising the deforestation and reducing the logistic costs of importation of tanning extracts.

The advantages of the technology can be summarised as follows:

- lower deforestation of some tree species
- maximum valorisation of a low profitable natural local source
- reduction of the energetic costs necessary for the concentration of the vegetable tannins by using technology of membranes
- reduction of logistic costs using local available vegetable extracts and avoiding overseas sources
- if technology of membranes is used, health related advantage by avoiding dust formation at workplaces in the tanning industry (substitution of powder-based product by liquid solution).