Hydrophilic-Core Microcapsules and their Formation

• US 20100320421A1
• Filed: 08/16/2010
• Published: 12/23/2010
• Est. Priority Date: 09/19/2005
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: LI, Wenyan, BUHROW, Jerry W., CALLE, Luz M., JOLLEY, Scott T.
• Granted Patent: US 9,227,221 B2
• Time in Patent Office: Days
• US Class Current: 252/388
• CPC Class Codes: B01J 13/14 Polymerisation; cross-linking
• CPC Class Codes: B01J 13/16 Interfacial polymerisation
• CPC Class Codes: B05D 2202/00 Metallic substrate
• CPC Class Codes: B05D 5/00 Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
• CPC Class Codes: B05D 5/06 to obtain multicolour or other optical effects B05D5/02 takes precedence
• CPC Class Codes: C04B 20/1029 Macromolecular compounds
• CPC Class Codes: C04B 2103/54 Pigments; Dyes
• CPC Class Codes: C04B 2103/61 Corrosion inhibitors
• CPC Class Codes: C04B 40/0641 Mechanical separation of ingredients, e.g. accelerator in breakable microcapsules
• CPC Class Codes: C08K 9/10 Encapsulated ingredients
• CPC Class Codes: C09B 67/0097 Dye preparations of special physical nature; Tablets, films, extrusion, microcapsules, sheets, pads, bags with dyes
• CPC Class Codes: C09D 5/082 characterised by the anti-corrosive pigment
• CPC Class Codes: C09D 7/41 Organic pigments; Organic dyes
• CPC Class Codes: C09D 7/48 Stabilisers against degradation by oxygen, light or heat
• CPC Class Codes: C09D 7/65 macromolecular C09D7/41-C09D7/48 take precedence
• CPC Class Codes: C09D 7/70 characterised by shape, e.g. fibres, flakes or microspheres

Abstract

Hydrophilic-core microcapsules and methods of their formation are provided. A hydrophilic-core microcapsule may include a shell that encapsulates water with the core substance dissolved or dispersed therein. The hydrophilic-core microcapsules may be formed from an emulsion having hydrophilic-phase droplets dispersed in a hydrophobic phase, with shell-forming compound contained in the hydrophilic phase or the hydrophobic phase and the core substance contained in the hydrophilic phase. The shells of the microcapsules may be capable of being broken down in response to being contacted by an alkali, e.g., produced during corrosion, contacting the shell.

Claims

1. A method of forming hydrophilic-core microcapsules with a shell capable of breaking down in response to alkaline conditions naturally occurring in the presence of corrosion, comprising:

forming a hydrophilic phase;

forming at least a first hydrophobic phase;

mixing the at least first hydrophobic phase with the hydrophilic phase to create and disperse droplets of the hydrophilic-phase within the at least first hydrophobic phase to form an emulsion; and

forming hydrophilic-core microcapsules.

2. The method of claim 1, including the further step of adding to the hydrophilic phase a dye, corrosion indicator, corrosion inhibitor, film-forming compound, healing agent, or combination thereof.

3. The method of claim 1, including the further step of adding a surfactant and a hydrophobic substance.

4. The method of claim 3, wherein the surfactant comprises alkyl anhydride.

5. The method of claim 3, wherein the hydrophobic substance comprises methyl myristate.

6. The method of claim 1, including the further step of adding a cross-linking agent comprising one or more ester and mercapto groups, and a shell wall forming pre-polymer or monomer.

7. The method of claim 6, wherein the cross-linking agent is selected from fully esterified monomers comprising ethyleneglycol di-2-mercapto acetate, ethyleneglycol di-2-hydroxyacetate, pentaerythritol tetrakis(2-hydroxyacetate), pentaerythritol tetrakis(3-hydroxypropionate) (PTT), pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol or tetrakis(3-mercaptopropionate), or from any number of partially esterified polyols comprising glycerol monoacetate, neopentylglycol monopropionate, or trimethylolpropane diacetate.

8. The method of claim 6, wherein the shell wall forming pre-polymer or monomer is selected from the group consisting of urea formaldehyde, melamine formaldehyde and other amine formaldehyde prepolymers, polyurethane prepolymers, polyols, isocyanates, urea and formaldehyde solution, melamine and formaldehyde solution, and other amine formaldehyde solutions.

9. The method of claim 1, including the further step of adding a catalyst to the emulsion.

10. The method of claim 9, wherein the catalyst is an acid.

11. The method of claim 10, including the further step of adding the acid catalyst until the emulsion has a pH in the range of about 2 to 5.

12. The method of claim 1, including the further step of heating the emulsion.

13. The method of claim 1, including the further step of mixing a second hydrophobic phase with the emulsion.

14. The method of claim 13, wherein the second hydrophobic phase includes a cross-linking agent comprising one or more ester groups.

15. The method of claim 14, wherein the second hydrophobic phase further includes a shell wall forming pre-polymer.

16. A method of forming hydrophilic-core microcapsules having shells capable of breaking down in response to alkaline conditions naturally occurring in the presence of corrosion, comprising:

forming a hydrophilic phase;

forming a hydrophobic phase;

mixing the hydrophobic phase with the hydrophilic phase to create and disperse hydrophilic-phase droplets within the hydrophobic phase to form an emulsion; and

forming hydrophilic-core microcapsules.

17. The method of claim 16, including the further step of adding to the hydrophilic phase a dye, corrosion indicator, corrosion inhibitor, film-forming compound, healing agent, or combination thereof.

18. The method of claim 16, including the further step of adding a water-soluble mixture of pre-polymers comprising a compound with one or more ester and mercapto groups.

19. The method of claim 18, wherein the compound with one or more ester and mercapto groups is selected from fully esterified monomers comprising ethyleneglycol di-2-mercapto acetate, ethyleneglycol di-2-hydroxyacetate, pentaerythritol tetrakis(2-hydroxyacetate), pentaerythritol tetrakis(3-hydroxypropionate) (PTT), pentaerythritol tetrakis(2-mercaptoacetate), or pentaerythritol tetrakis(3-mercaptopropionate), and their derivates or from partially esterified polyols comprising glycerol monoacetate, neopentylglycol monopropionate, or trimethylolpropane diacetate.

20. The method of claim 18, wherein the water-soluble mixture of pre-polymers further comprises a shell wall forming pre-polymer or monomer selected from the group consisting of urea formaldehyde, melamine formaldehyde and other amine formaldehyde prepolymers, polyurethane prepolymers, polyols, isocyanates, urea and formaldehyde solution, melamine and formaldehyde solution, and other amine formaldehyde solutions.

21. The method of claim 16, including the further the step of adding a surfactant and a hydrophobic substance.

22. The method of claim 21, wherein the surfactant comprises alkyl anhydride.

23. The method of claim 21, wherein the hydrophobic substance comprises methyl myristate.

24. The method of claim 16, including the further step of adding a catalyst to the emulsion.

25. The method of claim 24, including the further step of adding an acid catalyst to the emulsion.

26. The method of claim 25, including the further step of adding an acid catalyst until the emulsion has a pH in the range of about 2 to 5.

27. The method of claim 16, including the further step of heating the emulsion.

28. A method of forming hydrophilic-core microcapsules having shells capable of breaking down in response to alkaline conditions naturally occurring in the presence of corrosion, comprising:

forming a hydrophilic phase;

forming a first hydrophobic phase;

mixing the first hydrophobic phase with the hydrophilic phase to form an emulsion comprising droplets of the hydrophilic-phase dispersed in the first hydrophobic phase;

forming a second hydrophobic phase including a cross-linking agent comprising one or more ester groups;

mixing the second hydrophobic phase to said emulsion; and

forming hydrophilic-core microcapsules.

29. A hydrophilic-core microcapsule, comprising:

a shell formed of a material capable of breaking down in response to alkaline conditions naturally occurring in the presence of corrosion; and

a core material encapsulated within the shell, the core material comprising an active material.

30. The hydrophilic-core microcapsule of claim 29, wherein the shell comprises a copolymer having a cross-linking agent comprising one or more ester and mercapto groups, and a pre-polymer.

31. The hydrophilic-core microcapsule of claim 30, wherein the shell comprises about 5 percent to about 75 percent, by mass, cross-linking agent and about 25 percent to about 95 percent, by mass, pre-polymer.

32. The hydrophilic-core microcapsule of claim 30, wherein the shell comprises about 20 percent to about 50 percent, by mass, cross-linking agent and about 50 percent to about 80 percent, by mass, pre-polymer.

33. The hydrophilic-core microcapsule of claim 30, wherein the cross-linking agent is selected from the group consisting of fully esterified monomers comprising ethyleneglycol di-2-mercapto acetate, ethyleneglycol di-2-hydroxyacetate, pentaerythritol tetrakis(2-hydroxyacetate), pentaerythritol tetrakis(3-hydroxypropionate), pentaerythritol tetrakis(2-mercaptoacetate), or pentaerythritol tetrakis(3-mercaptopropionate), or from partially esterified polyols comprising glycerol monoacetate, neopentylglycol monopropionate, or trimethylolpropane diacetate.

34. The hydrophilic-core microcapsule of claim 30, wherein the pre-polymer is selected from the group consisting of urea formaldehyde, melamine formaldehyde and other amine formaldehyde prepolymers, polyurethane prepolymers, polyols, isocyanates, urea and formaldehyde solution, melamine and formaldehyde solution, and other amine formaldehyde solutions.

35. The hydrophilic-core microcapsule of claim 29, wherein the active material comprises at least one material selected from the group consisting of a corrosion inhibitor, a corrosion indicator, a film-forming compound, and a healing agent.

36. A coating, comprising:

a coating vehicle; and

hydrophilic-core microcapsules dispersed within the coating vehicle;

said hydrophilic-core microcapsules each having a shell formed from a material capable of breaking down in response to alkaline conditions naturally occurring in the presence of corrosion;

each of said shells including about 5 percent to about 75 percent, by mass, a cross-linking agent comprising ester and mercapto groups and about 25 percent to about 95 percent, by mass, a pre-polymer; and

a core material encapsulated within each of said shells, the core material selected from a group comprising a dye, corrosion indicator, corrosion inhibitor, film-forming compound, healing agent, or combination thereof.