Abstract

This new tannage is based on natural products, the plant polyphenols or vegetable tannins. The chemistry applies only to the condensed or catechol tannins, because it involves crosslinking the flavonoid ring system. The preferred vegetable tannin is mimosa, in which the presence of pyrogallol groups appears to aid the reaction. The preferred crosslinker is oxazolidine. High shrinkage temperature is achieved by heating to 60°C to drive the reaction; note, the pH requirements for fixing the two components of the tannage are mutually exclusive. Shrinkage temperatures > 110°C are easily achieved.