Patrick F. McIntyre

A comparison of the quality of carbon black dispersions prepared by dry and wet grind processes

ConclusionsWe have investigated the deflocculation mechanism of waterborne jet black dispersions made in the dry-grind process based on the two-roll milling. We also compared this dry-grind process with the conventional wet media grind process. As a result, we found that:(1)High jetness in the dry-grind process was found to result from complete surface coverage of the carbon black pigment with the acidic acrylic dispersant during the two-roll milling step. This complete surface coverage is achieved because the dry dispersant molecules before neutralization do not have electrostatic repulsion among them.(2)The amount of adsorption for the dry grind is three times as great as that for the wet grind.(3)The stabilization mechanism is due to steric repulsion imparted by the adsorbed dispersant molecules, and the electrostatic repulsion is an insignificant force for stabilization.(4)High temperature in the chip dissolution step lowers the jetness owing to the decrease in the solubility of the dispersant at higher temperatures.