High-pressure carbon dioxide tanning

The leather producing industry transforms untreated hides that may rot under wet conditions and are brittle under dry conditions into durable, imperishable leather by processes which incorporate tanning agents into the hides. Several steps of the tanning process can be intensified by high-pressure technology. Compressed carbon dioxide can be used to shorten tanning times, to reduce water effluents and pollution and to save leather-finishing-fats [E. Weidner, H. Geihsler, 1995, Verfahren zur Zurichtung von tierischen Häuten, DE 195 07 572 A 1]. This article focuses on the reduction of time of the process for the tanning step. Typically, about 30 h are used to tan skins with chrome. It is shown that the same tanning result is obtained in only 5 h if the process is performed under CO2-pressure between 30 and 100 bar. Based on a newly developed analytical method for monitoring the tanning success via the ion content in the tanning liquid the process principle and the acceleration of the tanning process is proven and demonstrated.