Abstract

The leather industry needs innovative products and processes to satisfy the requirements of a continuously evolving global market. Modern leathers are processed to very stringent technical specifications so that they will meet end use requirements. In most cases, to fulfil current demands for leather with very high fastness, the use of cross-linkers is needed. Due to the differences in the manufacturing processes of polyurethanes and acrylic binders, their structural differences, and the type of tanned and retanned leather being used, variations in cross-linking may occur. Quality discrepancies will therefore be observed in the finished leather. This study explores the influence of a cationic pre-bottom on the cross-linking reaction of polyaziridine, as well as the influence of the type of polymer employed and the type of tannage and retannage effected on the amount of cross-linker needed to improve wet physical properties of the finishing. A comparison of results shows that the application of a cationic pre-bottom improves fastness to wet rub, this improvement being most significant in polyurethane rather than in acrylic binders. Furthermore, the cationic prebottom provides better results when working with resin-synthetic-vegetable retanned leather and vegetable leathers. However, different amounts of polyaziridine are needed with regard to the content of carboxylic acid groups of the polymers being used.