Effect of Mixing Order of Keywords Polyvinylalchol, CMC And Optical Brightening Agent In a Normal Coating Color On Zeta Potential And Mixing Power/Energy, 1996 Coating Conference Proceedings

A typical coating color was made with English china clay as pigment. The mixing order of polyvinylalcohol (PVA), carboxymetbylcellulose (CMC) and the optical brightening agent (OBA) was varied. Four different PVA grades were chosen for the trials. The molecular mass varied from low to high viscosity products. Fully and partially hydrolyzed PVA grades were also tested. The mixing power and energy requirement were measured with a special shock meter which can record very accurately the power and energy required to mix a coating color. Shocks caused by different mixing orders could be detected and data was collected for further analysis. Zeta potential was measured after the addition of each chemical to find possible interactions. Zeta potential measurements and power energy recordings seem to provide new ways of evaluating the adsorption of water-soluble polymers on clay pigment in a coating color. The measurements provide a means of understanding the bridging caused by polymers. The tendency to obtain shocks was largely influenced by the mixing order and the degree of polymerization of the PVA. The flocculation, probably by bridging, is very strong when PVA with a high molecular weight is used. A shock was always detected when PVA was added as the first chemical into the clay slurry. If OBA and/or CMC were metered before PVA, the shocks were partially or almost totally eliminated. Zeta potential seemed to detect and indicate the changes in adsorption. The mixing power and energy required to produce a coating color varied with zeta potential readings and mixing order. The works show that changes in adsorption can be more accurately detected by implementing zeta potential and power/energy measurements in the production of coating colors.