Fungicidal treatment for ‘X-White’ tannage

Only small amounts of the product are sufficient to ensure that these organically tanned hides and skins, known as ‘X-Whites’, can be stored for longer periods. This means that, like chrome-tanned raw hides (wet-blues), they can be transported over greater distances, thus opening up new marketing opportunities.
To protect leather intermediates (wet-blue, wet-white, X-White) effectively against attack by fungi, it is essential to prevent fungal spores from growing both on the hides themselves. Hartmut Rehbein, Product Development in Lanxess’ Leather business unit, carried out extensive series of laboratory trials to investigate which fungicide provides the optimal protection.

Combination fungicide
For their laboratory trials, he examined numerous common fungicides, including both membrane-active substances, such as o-phenylphenol (OPP), p-chloro-m-cresol (PCMC) and sodium pyrithione, and intracellular, nucleophilic substances, such as octylisothiazolinone (OIT) and (2-thiocyanatomethylthio)benzothiazole (TCMBT).
Four widespread strains of microorganisms, namely the mold fungi Aspergillus niger, Aspergillus repens, Homoconis resinae and Trichoderma viride, which are known to attack leather, were used for the benchmark study. All the tests were conducted on the basis of the standardized ASTM 4576-08 process.
The combination product Preventol U-Tec G, which contains both the membrane-active components OPP and PCMC and the intracellular, nucleophilic active ingredient OIT, proved efficacy in every case. Even additions of as little as 0.25 %, calculated on the X-White weight, were found to be sufficient to prevent mold infestation for more than 28 days. In practice, this means that the leather intermediate (X-White) could be stored for up to six months. Without a fungicide, extensive mold growth is visible after only 10 days of storing.
Preventol U-Tec G has a number of further advantages, too, that fit perfectly with the Sustainable Leather Management concept. For example, all the ingredients are readily biodegradable in wastewater treatment plants. Additionally, the aromatic ingredients OPP and PCMC are distributed uniformly in the leather and fixed there via hydrogen bridges without tanning the collagen.
X-Tan is an organic tanning system that offers substantial improvements over conventional wet white manufacturing processes as regards both quality and ecology.
X-Tan is a sustainable tanning process that gives high-quality leather. It combines first-class performance with ecological advantages: for example, no reactive tanning materials remain in the leather or the effluent, and the salt load of the effluent is much lower than in conventional organic tannages.

A key feature of X-Tan is the relatively high whiteness of the leather, which makes it possible to obtain brilliant colors in the subsequent dyeing. The leather also has excellent physical fastness properties.
The new X-Tan technology is in keeping with the main goals of Lanxess’ Sustainable Leather Management initiative, which is designed to enhance and extend the company’s product portfolio for sustainable leather production.