PURPOSE: To obtain a pigment dispersion which gives an ink exhibiting no decrease in gloss in printing by making a lipophilic resin hydrophilic, emulsifying it in water, mixing it with a water-base suspension contg. a given amt. of a pigment, making it lipophilic again, and flushing the mixture.
CONSTITUTION: An emulsion is obtd. by dissolving a lipophilic resin (e.g. a rosin-modified phenol resin) having acidic or basic groups in an org. solvent (e.g. isopropyl alcohol) if necessary, neutralizing a part of or all the acidic or basic groups with a base or acid to make the resin hydrophilic, and emulsifying the resin in water. The emulsion is mixed with a water-base suspension of a pigment (e.g. carbon black) in such a manner that the amt. of the lipophilic resin dissolved as above or the amt. of the solid resin component in the solvent soln. is at least 70wt.% of the amt. of the pigment in the water-base suspension. An acid or base is added to the resultant mixture, contrary to the above neutralization step, to convert the resin lipophilic again, and the mixture is then subjected to flushing, thus giving a pigment dispersion.
ISHIMORI MOTOKAZU
TASHIRO NAMIYUKI
