On the subject of metal free, the chemical company Dermochimica proposes to the market Hydroil, a new line of products for the tanning and retanning process based on recovery waters coming from the production of olive oil. The new system, which obtained two patents, does not use metals but allows to obtain leathers with high-level characteristics and performance comparable to chrome tanning.

Specifically – the company explains – HYDROIL (i) is a product with high filling and retanning power, especially recommended for the retanning of wet-blue leather, eliminating synthetic resins and / or natural tannins. Thanks to the high concentration of natural antioxidant polyphenols (10 g / kg HYDROIL), higher than green tea, it is very effective in the inhibition of the formation of Cr (VI). Thanks to the multiple functions of HYDROIL (i) there is an overall saving of chemicals of 20-30%.
HYDROIL (p) is a product used as tanning agent which, added in combination with other tanning additives, is suitable for the production of items not only chrome-free, but also free of all other metals.

The metal-free articles obtained with HYDROIL (p) reach the same level characteristics of a chrome-tanned leather and on performances, is clearly superior to vegetable and aldehydes tanned leathers. Extremely versatile, it allows the production of all types of articles over every kind of leather.
The tanning process thus developed has demonstrated its effectiveness on leathers intended for any production segment, from footwear to automotive, from leather goods to furniture.

Worth to remember that Hydroil is the result of an Italian research project conducted through newco Tannow. Started a couple of years ago, the research was born with the aim of developing products of natural origin for the tanning sector, starting from the by-products of the agri-food industry. The proposed innovation was the following: re-use OMWW (Olive Mill Wastewater) to develop products with a tanning and antioxidant effect to make metal-free leathers and that are wet-blue base resistant to the formation of Cr VI. All this starting from a fundamental consideration: Italy is one of the most important world producers of leather goods and the second largest producer of olive oil in the world.
But let’s see how two industrial needs have happily met in a circular economy perspective. Olive Mill Wastewater (OMWW) derives from the production of olive oil and is among the most polluting agro-industrial wastewater, containing in reality phenol and polyphenolic compounds with a high antimicrobial and phytotoxic action and it would be a pity not to value them. The main phenolic compounds present in OMWW are hydroxytyrosol, tyrosol, catechol, methylcatechol, oleuropein, caffeic, gallic, vanillic and coumaric acid, which have extraordinary antioxidant properties. Among other things, natural tannins with tanning action are already present in OMWW. Consider that hydroxytyrosol can constitute up to 50% of total OMWW polyphenols and that is has been recognised as one of the most potent antioxidants in nature, about ten times greater than green tea and at least twice as high as CoQ10. And there is a huge quantity of olive mill wastewater, just think that from 100 kg olives are obtained 20-22 kg of olive oil and 50-80 kg of OMWW. At European level, in 2014/2015 were produced about 4.8 million tons of OMWW, which need to be disposed. Hence the solidity of the project also on an industrial level.

To conclude, the results of the research were in line with the best expectations. The tanning power of Hydroil turned out to be comparable to that of natural tannins. In addition, the antioxidant power of Hydroil on wet-blue retanning reduces the formation of Cr VI by 50% thus allowing the replacement of all synthetic retanning agents that contain formaldehyde.

Productions made in the tannery have given excellent results not only in terms of low environmental impact of the, completely metal-free, tanning process but also for the quality characteristics of the finished leather similar to those treated with chrome.