Method for coloring cellulosic materials using cationic pigment dispersion

Abstract

A method of coloring a cellulosic material which includes a) dispersing pulped cellulosic material into water; and b) coloring the pulped cellulosic material by adding a cationic dispersion to the water, where the dispersion includes: (i) at least one pigment; (ii) water; and (iii) at least one acid salt of a styrene maleimide resin in an amount effective to disperse the pigment. The cationic dispersion may be prepared by (i) mixing, at 500 to 10,000 rpm, at least one pigment; water; and either (a) at least one acid salt of a styrene maleimide imide resin or (b) at least one styrene maleimide imide resin in combination with at least one weak acid, thereby forming a dispersion premix; (ii) milling the dispersion premix in a mixer filled with ceramic, metal or glass beads for a period of time sufficient to reduce pigment agglomerates to primary particles, thereby forming a nonstandarized dispersion; and (iii) standardizing the dispersion against a color standard by adding water. The resulting cationic dispersion can be used to color cellulosic materials such as cotton and paper.