Method of preparing aqueous pigment dispersions

摘要

A process for preparing an aqueous pigment dispersion is provided in which a pigment, a coating agent, a grinding agent and a vehicle are subjected to grinding, followed by removal of the grinding agent and the vehicle to form a press cake, and dispersing the press cake to form a pigment dispersion. Also disclosed is an ink-jet ink containing an aqueous vehicle and the aqueous pigment dispersion thus made.

主权项

1. A process for making an aqueous pigment dispersion comprising the steps of:
(a) grinding a mixture comprising a pigment, one or a combination of coating agents, a grinding agent and a vehicle, wherein said grinding agent is insoluble in said vehicle and soluble in water, and said coating agents contain an ionizable moiety and have a structure of formula (I):
QM1]n  (I); (b) washing with an aqueous medium to remove said grinding agent to form a press cake; and (c) adding an aqueous vehicle, adjusting the pH to ionize said ionizable moiety on said coating agents, and dispersing said press cake from step (b), in this order or any other workable orders, to form a dispersion; wherein each M1 is COOH or NR1R2, or two M1 groups can be taken together with the carbon atoms they are bonded to form a cyclic anhydride, or M1 is OH when Q is C6-C40 aryl; n is an integer from 2 to 6; each R1 and R2 is independently H, C1-C9 alkyl or C3-C12 cycloalkyl; and Q is C6-C40 alkyl, C6-C40 substituted alkyl, C6-C40 aryl or Q is —Ar1—Y—Ar2— and forms a molecule of formula (II):wherein Ar1 and Ar2 are independently C6-C40 aryl; Y is CR3R4, S, S(O) or a straight bond; R3 and R4 are independently H or C1-C9 alkyl; each M2 is COOH, or two M2 groups can be taken together with the carbon atoms they are bonded to form a cyclic anhydride; and each m is independently an integer from 2 to 4.