Preparation of capsules

• US 9,005,494 B2
• Filed: 08/10/2009
• Issued: 04/14/2015
• Est. Priority Date: 01/20/2004
• Status: Active Grant

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: Valianatos, Peter J., Chebiyam, Rajesh, Manning, Jeremy J., Steiner, Michael L., Whitesides, Thomas H., Walls, Michael D.
• Primary Examiner(s): Seidleck, James J
• Assistant Examiner(s): POURBOHLOUL, SARIRA CAMILLA
• Application Number:
  US12/538,228
• Publication Number:
  US 20100044894A1
• Time in Patent Office: 2,073 Days
• Field of Search: 428402-40224, 428/403, 428/404, 428/407, 428/321.1, 428/474.4, 427/331, 427/389.9, 427/212, 427213-21336, 427/483, 427/256, 264/534, 264/5, 264/41, 264 4- 47, 424/400, 424/408, 424/450, 424/451, 424/455, 424/93.7, 424/184.1, 424/497, 424/489, 424/501, 424/490, 424/491, 424/492, 424/493, 424/494, 424/495
• US Class Current: 264/4.1
• CPC Class Codes: B01J 13/08 Simple coacervation, i.e. addition of highly hydrophilic material combined with spraying B01J13/043; combined with mechanical division B01J13/04
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]
• CPC Class Codes: Y10T 428/2984 Microcapsule with fluid core [includes liposome]
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2998 including synthetic resin or polymer

Abstract

Prior art processes for producing protein-based capsules (for example, capsules for use in electrophoretic media) tend to be wasteful because they produce many capsules outside the desired size range, which is typically about 20 to 50 μm. Capsule size distribution and yields can be improved by either (a) emulsifying a water-immiscible phase in a preformed coacervate of the protein; or (b) using a limited coalescence process with colloidal alumina as the surface-active particulate material.

Claims

1. A process for encapsulating a water-immiscible phase in a protein coacervate, the process consisting of:

forming a coacervate of the protein and a coacervating agent in an aqueous medium; and

thereafter, emulsifying the water-immiscible phase in the aqueous medium comprising the coacervate under conditions effective to cause deposition of the coacervate around the water-immiscible phase, thereby forming capsules of the water-immiscible phase surrounded by capsule walls of the coacervate.

2. A process according to claim 1 wherein the protein is gelatin.

3. A process according to claim 1 wherein the coacervating agent is acacia.

4. A process according to claim 1 wherein the water-immiscible phase comprises an aliphatic hydrocarbon.

5. A process according to claim 4 wherein the water-immiscible phase further comprises solid particles suspended in the hydrocarbon.

6. A process according to claim 5 wherein the solid particles are electrically charged.

7. A process according to claim 6 wherein the water-immiscible phase comprises two different types of solid particles bearing charges of opposite polarity.

8. A process according to claim 1 wherein at least part of the emulsification/capsule formation step is conducted at a temperature below about 35°

C.

11. A process according to claim 5 wherein the solid particles comprise titania.

12. A process according to claim 5 wherein the solid particles comprise carbon black.

13. A process according to claim 5 wherein the solid particles comprise copper chromite.

9. A process for encapsulating a water-immiscible phase in a protein coacervate, the process consisting of:

forming a coacervate of the protein and a coacervating agent in an aqueous medium;

thereafter, emulsifying the water-immiscible phase in the aqueous medium comprising the coacervate under conditions effective to cause deposition of the coacervate around the water-immiscible phase, thereby forming capsules of the water-immiscible phase surrounded by capsule walls of the coacervate; and

thereafter treating the capsules formed with a cross-linking agent effective to cause cross-linking of the protein.

10. A process according to claim 9 wherein the cross-linking agent is an aldehyde.

14. A process according to claim 10 wherein the aldehyde is glutaraldehyde.