Abstract

Liquid epoxide resins have an obvious potential as collagen crosslinkers, in particular as alternatives to the aldehydic-types currently used. In the work reported here, some conditions for the effective use of epoxides in tanning systems have been studied and identified based on hide powder trials. Few commercial aromatic epoxides were found to be water-soluble, and further, have relatively low reaction rates which is another disadvantage.

In a series of screening tests, it has been found that an epoxide with aromatic groups in its backbone, when used to treat collagen produces higher hydrothermal stability than collagen treated with an aliphatic epoxide. However, of the commercial aliphatic epoxide resins examined in this research, the water-soluble, tetra-functional sorbitol polyglycidyl ether, (e.g. Denacol EX 411), has been shown to be suitable for leather tannage applications.

Various types of waterborne epoxide resins, including emulsion and emulsifiable resins based on BDEGA (bisphenol A diglycidyl ether), have been examined but gave disappointing results. It is thought that difficulties lie in being unable to achieve good penetration into collagen’s fibrous structure of the particles of such emulsions. Late stage tannage, giving a leather product with high shrinkage temperature (Ts = 85°C) has been achieved; here the system required a catalyst to produce acceptable conversion within 3 hr at 50°C. The important factors influencing the effectiveness of a particular tannage, are discussed.