Composite particles and method for making the same

Patent metadata

Field	Value
Publication number	US-11614671-B2
Application number	US-202117548753-A
Country	US
Kind code	B2
Filing date	Dec 13, 2021
Priority date	Mar 20, 2017
Publication date	Mar 28, 2023
Grant date	Mar 28, 2023

Abstract

A composite particle is provided that comprises a base particle comprising at least a pigment or dye and cross-linked polyurea, a plurality of hydrophilic oligomeric groups, and a plurality of amine groups on the exterior portion of the base particle, and a steric stabilization polymer which is chemically bonded or physi-sorbed on the surface of the base particle. The cross-linked polyurea may form a network throughout the base particle. A method of making the composite particle includes providing either a solution containing a dye or a dispersion containing a pigment in a water-dispersible polyfunctional isocyanate dissolved in a water-miscible solvent, forming an emulsion of the solution/dispersion in water, agitating the emulsion while the polyfunctional isocyanate is converted into a cross-linked polyurea, and separating the composite particle containing the cross-linked polyurea and the dye/pigment from the emulsion.

First claim

We claim:

1. A method of making a composite particle comprising the steps:
mixing a dye or a pigment with a water-dispersible polyfunctional isocyanate in a water-miscible solvent to form a dye solution or a pigment dispersion, the water-dispersible polyfunctional isocyanate comprising a hydrophilic oligomeric group, wherein the hydrophilic oligomeric group comprises polyethylene oxide, and at least one isocyanate group;
adding the dye solution or the pigment dispersion to an aqueous phase to form an emulsion;
agitating the emulsion while the polyfunctional isocyanate is converted into a cross-linked polyurea by hydrolyzing isocyanate groups towards amine groups that react with unhydrolyzed isocyanate groups; and
separating the composite particles containing the cross-linked polyurea and the dye or pigment from the emulsion.

2. The method of claim 1 , wherein the cross-linked polyurea is formed by a monomer or oligomer of water-dispersible polyfunctional isocyanate.

3. The method of claim 1 , wherein the water-dispersible polyfunctional isocyanate has NCO content of about 5 to 35%.

4. The method of claim 1 , wherein the cross-linked polyurea of the composite particles comprises amine groups.

5. The method of claim 4 , further comprising a step of forming a stabilizing polymer on the surface of the composite particle, the stabilizing polymer being covalently bonded to the cross-linked polyurea.

6. The method of claim 5 , wherein the step of forming the stabilizing polymer comprises (a) reacting an amine group of the cross-linked polyurea with a first reagent, the first reagent comprising a first functional group capable of reacting with the amine group of the cross-linked polyurea and a second polymerizable functional group, and (b) reacting the product of step (a) with a second monomer or oligomer under conditions effective to cause reaction between the second polymerizable functional group and the second monomer or oligomer.

7. The method of claim 6 , wherein the first functional group of the first reagent is an electrophilic group.

8. The method of claim 6 , wherein the second polymerizable functional group of the first reagent is an acrylate functional group, a methacrylate functional group or a vinyl functional group.

9. The method of claim 5 , wherein the step of forming the stabilizing polymer comprises (a) reacting an amine group of the cross-linked polyurea with a second reagent, the second reagent comprising a first functional group capable of reacting with the amine group of the cross-linked polyurea and a third polymerization initiation functional group, and (b) reacting the product of step (a) with a third monomer or oligomer under conditions effective to cause reaction between the third polymerization initiating functional group and the third monomer or oligomer.

10. The method of claim 9 , wherein the third polymerizable functional group of the second reagent is an acrylate functional group, a methacrylate functional group or a vinyl functional group.

11. The method of claim 1 , wherein the hydrophilic oligomeric group is aliphatic.

12. The method of claim 1 , wherein the water-miscible solvent has a water solubility of at least 25% by weight.

13. The method of claim 1 , wherein the dye is insoluble in water and soluble in the water-miscible solvent.

14. The method of claim 13 , wherein the dye is selected from the group consisting of Solvent Blue 70, Solvent Blue 67, Solvent Blue 136, Solvent Red 127, Solvent Red 130, Solvent Red 233, Solvent Red 125, Solvent Red 122, Solvent Yellow 88, Solvent Yellow 146, Solvent Yellow 25, Solvent Yellow 89, Solvent Orange 11, Solvent Orange 99, Solvent Brown 42, Solvent Brown 43, Solvent Brown 44, Solvent Black 28, Solvent Black 29, and combinations thereof.

15. The method of claim 1 , further comprising a step of forming a stabilizing polymer on the surface of the composite particle, the stabilizing polymer being physi-sorbed to the cross-linked polyurea.

16. The method of claim 15 , wherein the steric stabilizing polymer is formed via dispersion polymerization.

17. The method of claim 16 , wherein the steric stabilizing polymer is formed via living radical dispersion polymerization.

18. The method of claim 15 , wherein the stabilizing polymer is formed by treating the cross-linked polyurea with a solution having a fourth monomer or oligomer under conditions effective to polymerize the fourth monomer or oligomer.

19. The method of claim 15 , wherein the composite particle is formed by (a) coating the cross-linked polyurea with silica, (b) treating the silica coated particle with a third reagent comprising a silane coupling group and a fourth polymerizable functional group, and (c) treating the product of step (b) with a fifth monomer or oligomer to cause reaction between the fourth polymerizable functional group and the fifth monomer or oligomer.

Assignees

• E Ink Corp

Inventors

• Telfer Stephen J
• Herb Craig A
• Yezek Lee

Classifications

• G02F1/167 Primary

  by electrophoresis · CPC title

• C08K5/0091

  Complexes with metal-heteroatom-bonds · CPC title

• G02F2001/1678

  characterised by the composition or particle type · CPC title