Patent ID: 7737196

Claim:
A method of making a passivated pigment dispersion, comprising the steps: a) dispersing pigment particles in an aqueous liquid vehicle to form a pigment dispersion; b) introducing a first monomer and a second monomer into a water-miscible solvent in which the first monomer and the second monomer polymerize to form a passivation coating solution containing a polymer precursor including at least one urethane linkage or urea linkage, wherein polymerization is initiated separately from the pigment dispersion; c) forming a passivation layer on the surface of the pigment particles by adding the passivation coating solution to the pigment dispersion so that the polymer precursor substantially uniformly coats the pigment particles, thereby creating a passivated pigment dispersion; and d) polymerizing at least one encapsulation monomer in the passivated pigment dispersion, said at least one monomer forming a polymer-encapsulation layer deposited on or attached to the passivation layer, thereby forming a polymer-encapsulation pigment, wherein the at least one encapsulation monomer is selected from the group consisting of styrene, p-methyl styrene, methyl methacrylate, hexyl acrylate, hexyl methacrylate, butyl acrylate, butyl methacrylate, ethyl acrylate, hydroxyethyl acrylate, ethyl methacrylate, hydroxyethyl methacrylate, propyl acrylate, hydroxypropyl acrylate, propyl methacrylate, hydroxypropyl methacrylate, vinylbenzyl chloride, and combinations thereof.