Grinding of pigments

Abstract

A method of salt grinding of pigments wherein the material to be ground is milled with a salt, an organic conditioner, and larger particles such as balls, nails, or in a strong kneader for comminuting the pigment to the desired state of subdivision. This grinding mass is made into a smooth flowing suspension by addition of more organic conditioning agent rather than solvents, as heretofore. The suspension is then passed through a decanter type centrifuge resulting in a sediment fraction containing most of the salt, some pigment, and some organic conditioning agent, and a liquid fraction containing most of the pigment, some salt and conditioning agent. The sediment portion is returned to the grinding mechanism where it is combined with a new batch of unmilled pigment for a subsequent milling cycle, while the pigment is separated by filtration from the liquid portion after some addition of water and flocculating agents. The filtration and wash liquors are combined. After evaporation, these liquors are then used for thinning out of the milling mass of a subsequent batch.

Dependencies are inferred from the claim text.