Water-in-oil microencapsulation process and microcapsules produced thereby

• US 6,113,935 A
• Filed: 12/19/1997
• Issued: 09/05/2000
• Est. Priority Date: 12/31/1996
• Status: Expired due to Fees

• Current Assignee: Zeneca Incorporated (Astrazeneca PLC)
• Original Assignee: Zeneca Incorporated (Astrazeneca PLC)
• Inventors: Rodson, Maurius, Scher, Herbert B.
• Primary Examiner(s): Page, Thurman K.
• Assistant Examiner(s): WARE, TODD
• Application Number:
  US08/994,316
• Time in Patent Office: 991 Days
• Field of Search: 264/4.7, 424/408, 424/457, 424/497
• US Class Current: 424/408
• CPC Class Codes: A01N 2300/00 Combinations or mixtures of active ingredients covered by classes A01N27/00 - A01N65/48 with other active or formulation relevant ingredients, e.g. specific carrier materials or surfactants, covered by classes A01N25/00 - A01N65/48
• CPC Class Codes: A01N 25/18 Vapour or smoke emitting compositions with delayed or sustained release
• CPC Class Codes: A01N 43/40 six-membered rings
• CPC Class Codes: A61K 9/5031 obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polyethylene glycol, poly(lactide-co-glycolide)
• CPC Class Codes: B01J 13/16 Interfacial polymerisation

Abstract

A suspension of microcapsules in an organic liquid, the microcapsules containing an aqueous phase, is produced by interfacial polymerization in the presence of a proton transfer catalyst of a water-in-oil emulsion in which the aqueous phase contains a urea/formaldehyde or melamine/formaldehyde prepolymer.

Claims

1. A process for the production of microcapsules containing an aqueous material within a polymeric shell, said process comprising:

(a) providing an aqueous phase comprising a material to be encapsulated, and a urea-formaldehyde and/or melamine-formaldehyde prepolymer dissolved therein;

(b) creating an emulsion of said aqueous phase in a continuous organic liquid phase comprising one or more organic solvents and one or more surface active agents, wherein the emulsion comprises discrete droplets of the aqueous phase dispersed in the continuous phase organic liquid, there being formed thereby an interface between the discrete droplets of the aqueous phase and the continuous organic liquid phase; and

(c) causing in situ self-condensation of the prepolymer in the aqueous phase of the discrete droplets adjacent to the interface by heating the emulsion to a temperature of from about 20 to about 100°

C. in the presence of a surface active proton transfer catalyst which is soluble in the organic liquid but only slightly soluble in the aqueous phase for a sufficient period of time to allow substantial completion of in situ condensation of the prepolymer to convert the liquid droplets of the aqueous phase to microcapsules consisting of solid permeable polymer enclosing the aqueous material.

2. A process according to claim 1 in which the aqueous material contains an active ingredient dissolved and/or dispersed therein.

3. A process according to claim 1 in which the aqueous material contains an active ingredient dissolved therein.

4. A process according to claim 1 in which the aqueous material contains an active ingredient dispersed therein.

5. A process according to claim 3 in which the active ingredient is a bioactive material.

6. A process according to claim 5 in which the bioactive material is a pesticide.

7. A process according to claim 6 in which the bioactive material is a herbicide.

8. A process according to claim 7 in which the herbicide is paraquat.

9. A process according to claim 1 in which the organic liquid contains an active ingredient.

10. A process according to claim 9 in which the active ingredient is dissolved in the organic liquid.

11. A process according to claim 9 in which the active ingredient is dispersed in the organic liquid.

12. Microcapsules produced according to the process of claim 1.

13. A suspension of microcapsules in an organic liquid produced according to the process of claim 1.

14. Microcapsules comprising a polymeric shell wall formed of urea-formaldehyde and/or melamine-formaldehyde polymer containing an aqueous material.

15. Microcapsules according to claim 14 wherein the aqueous material comprises a water-soluble or water-dispersible bioactive material.

16. Microcapsules according to claim 15 wherein the bioactive material is a pesticide.

17. Microcapsules according to claim 15 wherein the bioactive material is a herbicide.

18. Microcapsules according to claim 17 wherein the herbicide is paraquat.

19. Microcapsules according to claim 14 wherein the microcapsules are suspended in an organic liquid.

27. A packaged pesticidal formulation comprising microcapsules according to claim 14 contained within a water-soluble packaging material.

20. A suspension of microcapsules comprising an organic liquid with microcapsules suspended therein, and wherein the microcapsules are further comprised of a polymeric shell wall formed of urea-formaldehyde and/or melamine-formaldehyde polymer containing a water-soluble or water-dispersible bioactive material.

21. A microcapsule suspension according to claim 20 wherein the microcapsules contain a water-soluble or water-dispersible pesticide.

22. A microcapsule suspension according to claim 21 wherein the pesticide is a herbicide.

23. A microcapsule suspension according to claim 20 wherein the organic liquid contains a substantially water-insoluble pesticide.

24. A microcapsule suspension according to claim 23 wherein the substantially water-insoluble pesticide is a herbicide.

25. A microcapsule suspension according to claim 23 wherein the substantially water-insoluble pesticide is an insecticide.

26. A microcapsule suspension according to claim 23 wherein the substantially water-insoluble pesticide is a fungicide.

28. A packaged pesticidal formulation comprising a microcapsule suspension according to claim 21 contained within a water-soluble packaging material.

29. A packaged pesticidal formulation comprising a microcapsule suspension according to claim 23 contained within a water-soluble packaging material.