Zero order release and temperature-controlled microcapsules and process for the preparation thereof

• US 6,544,646 B2
• Filed: 04/27/2001
• Issued: 04/08/2003
• Est. Priority Date: 04/27/2000
• Status: Expired due to Fees

• Current Assignee: Verizon Incorporated (Verizon Communications Inc.)
• Original Assignee: Verizon Incorporated (Verizon Communications Inc.)
• Inventors: Nalamothu, Vijendra, Lee, Jeffry, Vaghefi, Farid
• Primary Examiner(s): Acquah, Samuel A.
• Application Number:
  US09/844,064
• Publication Number:
  US 20010044026A1
• Time in Patent Office: 711 Days
• Field of Search: 264/4.3, 264/4.32, 264/4.4, 264/7, 264/13, 428/402.24, 428/403
• US Class Current: 428/402.24
• CPC Class Codes: A61K 9/1617 Organic compounds, e.g. phospholipids, fats
• CPC Class Codes: A61K 9/1652 Polysaccharides, e.g. alginate, cellulose derivatives; Cyclodextrin homeopathic globules A61K9/1623
• CPC Class Codes: A61K 9/1694 resulting in granules or microspheres of the matrix type containing more than 5% of excipient
• CPC Class Codes: A61K 9/5015 Organic compounds, e.g. fats, sugars
• CPC Class Codes: B01J 13/04 by physical processes, e.g. drying, spraying
• CPC Class Codes: B01J 13/22 Coating
• CPC Class Codes: Y10T 428/2984 Microcapsule with fluid core [includes liposome]
• CPC Class Codes: Y10T 428/2989 Microcapsule with solid core [includes liposome]
• CPC Class Codes: Y10T 428/2991 Coated

Abstract

A microcapsule composition comprising a core material in a matrix of polymorphic shell material, releases said core material in an aqueous environment in accordance with zero order linear release profile. A preferred composition comprises a core material having a degree of water solubility entrapped in a beta crystalline matrix of water insoluble shell material which matrix may, optionally, be surrounded by a contiguous core material-free layer of water insoluble shell material. Also disclosed is a process for the preparation of microcapsules comprising subjecting a flowable mixture of core material and a first amount of water insoluble shell material to a pressure force to form a pressure-treated mixture, and passing said pressure-treated mixture through a spray nozzle into a chilling zone to form a solidified composition. A special embodiment of the method providing for the long term moisture stability of the resulting microcapsules subjects the microcapsules prepared in the first step to a second coating with a second amount of water insoluble shell material.

Claims

1. A process for the manufacture of a water insoluble composition comprising a core material and a water insoluble shell material comprising:

a. subjecting a flowable mixture of core material and a first amount of water insoluble shell material to a pressure force to form a pressure-treated mixture; and

b. spraying said pressure-treated mixture into a chilling zone to form a solidified composition.

2. A process according to claim 1 wherein said core material comprises solid particles.

3. A process according to claim 2 where said microcapsules are substantially spherical and have a mean particle size of from about 5 to about 400 microns.

4. A process according to claim 1 wherein said shell materials are polymorphic materials capable of solidifying into more than one crystalline form.

5. A process according to claim 4 wherein said water insoluble shell material comprises a mixture of two or more polymorphic materials.

6. A process according to claim 5 wherein said shell materials are polymorphic waxes.

7. A process according to claim 1 wherein said flowable mixture is maintained at a temperature above the solidification temperature of said shell material.

8. A process according to claim 7 wherein said mixture is maintained below the melting temperature of said shell material.

9. A process according to claim 8 wherein said shell material exhibits a melting curve where melting begins at T1 and is substantially complete at T2, and exhibits a cooling curve where solidification begins at T3 and is substantially complete at T4, wherein T3 is less than T1.

10. A process according to claim 9 wherein the difference between T1 and T2 is determined by the ratio of components comprising said shell material.

11. A process according to claim 1 wherein said composition is contacted with a second amount of a water insoluble shell material.

12. A process according to claim 11 wherein said composition is spray coated with a said second amount of shell material.

13. A process according to claim 12 wherein said second amount of shell material is from about 5 to about 30 percent by weight of the amount of shell material used to form said solidified composition.

14. A process according to claim 13 wherein said second amount of shell material is about 10 percent by weight of said first amount of shell material.

15. A process according to claim 12 wherein said first and second amounts of shell material comprise the same shell material.

16. A process according to claim 1 wherein said pressure force is applied for less than a second at a pressure of from about 2,000 psi to about 20,000 psi.

17. A process according to claim 1 wherein said pressure force is applied to said mixture which is passed through a chamber that subjects said mixture to cavitation and/or shear forces.

18. A process according to claim 2 wherein said particles comprise sodium bicarbonate.

19. A process according to claim 9 wherein the melting point of said shell composition starts at about 106 degrees F. and is substantially complete at about 135 degrees F.

20. A sodium bicarbonate microcapsule produced in accordance with claim 1.

21. A sodium bicarbonate microcapsule in accordance with claim 20 characterized in that said capsule releases less than about 2.5% of bicarbonate in an aqueous medium at room temperature in about one hour.

22. A microcapsule comprising a core material in a matrix of polymorphic shell material, where, in an aqueous environment, said core material is released from said microcapsule in accordance with zero order linear release profile.

23. A microcapsule according to claim 22 wherein said core material is an acid or basic salt of an organic compound.

24. A microcapsule according to claim 23 wherein said core material has a mean particle size of between about 250 to about 400 microns.

25. A microcapsule according to claim 24 wherein said microcapsules are substantially spherical.

26. A microcapsule according to claim 25 wherein said shell material is a polymorphic wax or a mixture of polymorphic waxes.

27. A microcapsule according to claim 25 wherein said organic compound is released from said shell at a substantially linear rate for about 8 to about 24 hours.

28. A storage stable microcapsule composition comprising a core material in a beta crystalline matrix of water insoluble polymorphic material which matrix is surrounded by a contiguous layer of water insoluble polymorphic material free of core material, wherein said core material is capable of being released from said microcapsule in a pre-defined temperature range.

29. A storage stable composition according to claim 28 wherein said core material is a water soluble inorganic compound.

30. A composition according to claim 29 wherein said core material comprises solid particles having a mean particle size of from about 5 to about 100 microns.