Self-dispersed pigments and methods for making and using the same
A method of modifying a pigment that includes reacting a reactive compound having an X—[Y] n reactive group with a secondary compound N—S—ZM to form a substituted reactive intermediate [Y] a —X—(N—S—ZM) b . A pigment is reacted with the substituted reactive intermediate [Y] a —X—(N—S—ZM) b to attach the substituted reactive intermediate to the surface of the pigment to form a surface modified pigment. X may be a sulfonyl, phosphoryl, or 1,3,5-triazinyl group, Y may be a halogen leaving group, N may be a basic nucleophilic group, S may be an organic group, and ZM may be an ionizable end group. Also, n is an integer between 1 and 3, b is an integer between 1 and 3, and a=n−b. When n is equal to or greater than b, and if b is 2 or 3, each N—S—ZM can be the same or different.
1. A method of modifying a pigment, the method comprising:
attaching a reactive group X—Y to a surface of a pigment; and
subsequently displacing Y with an organic substrate N—S—ZM to form a surface-modified pigment having attached X—N—S—ZM;
wherein X is a sulfonyl, phosphoryl, or 1,3,5-triazine group;
Y is fluorine, chlorine, bromine, or iodine;
N is an amine, an imine, a pyridine, or a thiol group;
S is substituted or unsubstituted alkyls, aryls, or polymer chains having a molecular weight range from about 300 to about 8000;
Z is a carboxyl, sulfonyl, phenolic, phosphoryl, ammonium, trimethylammonium, or tributylammonium group; and
M is a halide, a negatively charged ion, a proton in salt form, or a cation in salt form.
2. The method of claim 1 , wherein X is a sulfonyl group.
3. The method of claim 2 , wherein the reactive group X—Y is attached to the surface of the pigment by chlorosulfonation with a chlorosulfonating agent comprising chlorosulfonic acid, thionyl chloride, or a combination thereof.
4. The method of claim 3 , wherein the ratio of pigment to chlorosulfonating agent is at least about 4:1 (wt/wt).
5. The method of claim 3 , wherein the ratio of pigment to chlorosulfonating agent is from about 1:20 to about 1:1 (wt/wt).
6. The method of claim 3 , wherein the chlorosulfonating agent is a mixture of chlorosulfonic acid and thionyl chloride in a ratio of about 3:1 to about 6:1 (wt/wt).
7. The method of claim 3 , wherein the chlorosulfonation is carried out at a temperature of about 25° C. to about 160° C.
8. The method of claim 2 , further comprising:
modifying a majority of the pigment surface to form a liquid gel; and
subsequently milling the liquid gel with excess untreated pigment and water to form a stable aqueous pigment dispersion.
9. The method of claim 8 , wherein the modifying the majority of the pigment surface comprises chlorosulfonating a pigment at a temperature of at least about 90° C. for at least about one hour to form a pigment sulfonyl chloride.