Abstract

In the upgrading of tannery solid wastes, the commercial application of the by-products obtained is the key to attractive technological alternatives.

In the particular case of chrome shavings hydrolysed by an alkaline-enzyme process, the uses of collagen hydrolysate (CH) are the driving force for the start-up of a project when consideration is given to the amounts generated and to the diversity of applications, in addition to the fact that basic chrome salts -obtained from the dissolution of the chrome cake – may be used as trouble-free assistants to the fresh tanning agent.

The present paper, which follows the Part I of this study; “Collagen Hydrolysate: ‘soluble skin’ applied in post-tanning processes I. Characterisation” (JSLTC, 2000, 84,29) shows the experimental results obtained from the manufacture of various types of bovine leathers carried out at the CITEC pilot plant and in tanneries using CH in the post-tanning processes. In addition, the interactions of CH with acrylic retanning agents, studied at laboratory scale, are included.

CH performs in a synergistic fashion with various retanning agents. In addition to its cosmetic-lubricating effect which enhances the leather grain properties and provides greater softness improving the resistance of the fibrous tissue, there is also a ‘restoring effect’ upon the grain surface of the semi-finished leather, masking preservation defects and damage marks on the skin. The interaction with dyes is evident from the intensified colours and improved homogeneity of the dyeing.

CITEC has developed, besides CH, a copolymer CH-acrylic acid: “acrylic-protein” retanning agent MCH-106, that shows good properties in the development of full grain leather and splits. The application of the CH and the acrylic-protein MCH-106 in processing full-grain leather generates leathers of similar or higher quality to the standard one.

The application of CH in leather manufacture is an attractive response to the question of how to use the byproducts derived from the treatment of the chrome shavings.