Prediction of Performances of Some Aqueous Pigment Dispersions for Leather Finishing

摘要

Quality of leather is given by the finishing operation.When aqueous pigment dispersions are used as finishing and roller coating as method of application,the aspect of leather depends both on viscosity and surface tension of dispersion.Rheological behaviour of ten aqueous pigment dispersions was studied and surface tension measured in order to predict their quality as leather finishing from the flow and surface characteristics.It was found that two dispersions - Casicolor Brown R and Blue OM - behave as ideal plastic fluids onto the whole accessible shearing rate range,four - Casicolor Black,White C,Brown S and Bordeaux S-have time independent pseudoplastic behaviour,while the other four- Casicolor Ochre,Echo-Yellow Medium,Red BL and Echo-Cherry Red,with higher viscosities,have pseudoplastic behaviour and are more or less thixotropic.The higher the viscosity the most pronounced the thixotropy.Surface tensions,as important as viscosities in avoiding of ribbing,combined with rheological behaviour shows that the most advantageous from the point of view of application as leather finishing are the viscous thixotropic aqueous pigment dispersions Casicolor Echo-Yellow Medium and Casicolor Ochre.Their high viscosity ensures that the finish does not come off the roller onto the leather and high surface tension and low levelling viscosity,determined by their thixotropy,reduce the likelihood of ribbing.