Method of preparing cross-linked colorant dispersions
View Patent ↗A process for preparing a crossed-linked colorant dispersion is provided in which a partially neutralized dispersant polymer having a cross-linkable moiety is used as a dispersant for a colorant by reacting the cross-linkable moiety on the dispersant with a cross-linking agent.
1. A process for making a cross-linked colorant dispersion comprising the steps of:
(a) dispersing a colorant in an aqueous vehicle with a partially neutralized dispersant polymer having a cross-linkable moiety, wherein said dispersant polymer is adsorbed to the colorant, and the percentage of the remaining un-adsorbed dispersant polymer is less than 20% of the colorant by weight based on the total weight of the colorant;
(b) reacting the cross-linkable moiety on the dispersant with a cross-linking agent; and
(c) adjusting the pH of the aqueous vehicle to greater than 8.
2. The process of claim 1 , further comprises a step of purifying the dispersion by ultrafiltration after step (a) or step (c).
3. The process of claim 1 , wherein the percentage of the un-adsorbed dispersant polymer is less than 10% of the colorant by weight based on the total weight of the colorant.
4. The process of claim 1 , wherein the percentage of the un-adsorbed dispersant polymer is less than 5% of the colorant by weight based on the total weight of the colorant.
5. The process of claim 4 , wherein the pH of the aqueous vehicle is adjusted to between 8 and 10.5 in step (c).
6. The process of claim 1 , wherein the cross-linking agent is one or more members selected from the group consisting of epoxide, isocyanate, carbodiimide, N-methylol, oxazoline, silane, and mixtures thereof.
7. The process of claim 6 , wherein the pH is between 8 and 10.5.
8. The process of claim 1 , wherein the dispersant polymer is neutralized to 30%.
9. The process of claim 1 , wherein tyre dispersant polymer is neutralized to 50%.
10. The process of claim 1 , wherein the dispersant polymer is neutralized to 70%.
11. The process of claim 1 , wherein the dispersant polymer is selected from the group consisting of polyurethane, polyvinyl and polyester.
12. The process of claim 11 , wherein the dispersant polymer is polyurethane.
13. The process of claim 11 , wherein the dispersant polymer is polyvinyl.
14. The process of claim 1 , wherein the cross-linkable moiety on the dispersant polymer is one or more members selected from the group consisting of acid, hydroxyl, amino, and mixtures thereof.
15. The process of claim 4 , wherein the cross-linkable moiety on the dispersant polymer is acid.
16. The process of claim 15 , wherein the cross-linking agent is epoxide.
17. The process of claim 15 , wherein the cross-linking agent isocyanate.
18. The process of claim 1 , wherein the mole ratio of the cross-linkable moiety on the dispersant polymer to the cross-linking agent is from 15:1 to 1:1.5.
19. The process of claim 18 , wherein the mole ratio of the cross-linkable moiety on the dispersant polymer to the cross-linking agent is from 9:1 to 1:1.1.
20. The process of claim 19 , wherein the mole ratio of the cross-linkable moiety on the dispersant polymer to the cross-linking agent is from 8:1 to 1:1.