Clariant’s EasyWhiteTan in post-tanning30 September 2011
Clariant’s new EasyWhiteTan system not only meets the demands of the wet-end tanning process but the leather produced can also be easily used in post-tanning or retanning operations. Compared with chrome-free automotive leather, leathers produced with EasyWhite Tan show the same properties and no adjustments are necessary, according to Clariant, one of the leading suppliers of leather chemicals. The crust characteristics for other articles, which are more difficult to produce with existing chrome-free systems, can easily be achieved with the new tanning system. In many cases, the characteristics are similar to conventional chrome tanned leather. Tanners of shoe upper leather have found EasyWhite Tan crust leathers well suited to their sector.
Because most retanning agents, dyes and fatliquors have been developed for application on wet-blue leathers, the main problems with conventional wet-white leather have been associated with the reactivity of the wet-white itself and the fixation of post-tanning products. Often, due to the desired characteristics of the final articles, an excess of these products is necessary to approach chrome leather characteristics. This has a severe impact on the wastewaters with unfixed products and on the physical properties of the final leather produced. EasyWhite Tan, however, has a cationic character and presents new opportunities for retanning, dyeing and fatliquoring of chrome-free leathers with appropriate post-tanning products and treatment. The leathers produced with Clariant’s new tanning process have less stretch and elasticity, with fewer wrinkles and flatter growth marks. Besides having a tight, fine grain, 20% less dyestuffs are required than with conventional wet white. They also have higher light and heat resistance and have no negative influence on water resistant leather if re-chroming is applied.
The EasyWhite Tan process has multiple advantages for processing raw hides; it uses less water, reduces environmental load and wastewater treatment, requires no added salt, and it removes two or three process stages, including the pickle and basification steps. It is also metal, aldehyde and phenol free.
The processing of chrome-free or wet-white leather, however, was, until the advent of the new tanning system, considered to be somewhat difficult. EasyWhite Tan is based on Clariant’s Granofin Easy F-90, a single, easy-to-use liquid tanning agent.