Rapid and high exhausted coloration technology: Dyeing of bovine hides under vacuum

In the current study, the aim was to improve the dyeing properties of wet-blue and crust leathers under vacuum conditions, increasing the dyestuff exhaustion, and thus obtaining environmental and economic gains. In this context, dyeing was performed using conventional dyestuff and water ratios in a vacuum environment with 20 kPa pressure, and the leathers produced as the control group in non-vacuum conditions were compared in terms of dye exhaustion and colour measurements. Dye concentrations in wastewaters were measured spectrophotometrically and dye exhaustions were calculated. L*, a* and b* values, colour difference (Delta E) and colour intensity (K/S) in dyed leathers were determined. According to the results, it was determined that the dyestuff exhaustion increased with the vacuum application, and accordingly, the colour properties of the leather improved. The highest exhaustions were obtained from the water-free application and 25% dye-reduction and water-free trials used in the dyeing process, with a final uptake of 93.7%. As a result, by performing the dyeing process under vacuum conditions, the colour properties of the finished leathers could be improved, the amount of dyestuff in the wastewater could be reduced, and the water usage rates could be reduced.