COATING PROCESS TO PRODUCE CONTROLLED RELEASE COATINGS

Abstract

An aqueous polymer coating composition containing at least one latex or pseudolatex is coated on a substrate in a high humidity coating process followed by heat treatment of the coated substrate above the film forming temperature of the coating at low humidity. The coated substrate gives a stable reproducible dissolution profile substantially insensitive to temperature or humidity conditions upon storage. The high humidity coating process is achieved by addition of water to the coating chamber through dilution of the coating formulation or humidification of inlet air. Contrary to the conventional low humidity coating process, residual water is retained in the coating layer of the coated substrates in the coating step. When the coated substrates are heat treated at a temperature greater than the minimum film forming temperature, the residual water in the coating layer will ensure adequate capillary force for the completion of film coalescence. High humidity heat treatment is not needed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the effect of curing conditions on theophylline release from coated pellets (high humidity coating, 4% coating weight gain).

FIG. 2 shows the lack of effect of humidity during curing on release from coated pellets (high- humidity coating 2% coating weight gain).

FIG. 3 shows the effect of curing time on theophylline release from coated pellets (high humidity, 1.5% coating weight gain).

Claims

1. A process for coating a substrate with aqueous polymer coating composition comprising the steps of: (i) coating said substrate with said aqueous polymer coating composition under high relative humidity conditions followed by,(ii) a heat treatment step; wherein said heat treatment step is conducted under low humidity conditions, and said aqueous polymer coating composition comprises a latex or pseudolatex film former.

2. The process of claim 1, wherein the aqueous polymer coating composition further comprises a plasticizer.

3. The process of claim 2, wherein said high humidity is greater than 40% relative humidity.

4. The process of claim 2, wherein high humidity is greater than 50% relative humidity.

5. The process of claim 2, wherein high humidity is greater than 60% relative humidity.

6. The process of claim 2, wherein high humidity is greater than 70% relative humidity.

7. The process of claim 2, wherein high humidity is greater than 80% relative humidity

8. The process of claim 2, wherein high humidity is greater than 90% relative humidity.

9. The process of claim 2, wherein said low humidity is less than 16 grams of water/kg of air.

10. The process of claim 2, wherein said low humidity is less than 10 grams of water/kg of air.

11. The process of claim 2, wherein said low humidity is less than 8 grams of water/kg of air.

12. The process of claim 2, wherein said low humidity is less than 5 grams of water/kg of air.

13. The process of claim 2, wherein said low humidity is less than 3 grams of water/kg of air.

14. The process of claim 2, wherein said heat treatment step is conducted at a temperature above a minimum film forming temperature of said aqueous polymer coating composition.

15. The process of claim 2, wherein said heat treatment step is conducted at a temperature above 40° C.

16. The process of claim 2, wherein said heat treatment step is conducted at a temperature above 60° C.

17. The process of claim 2, wherein said heat treatment step is conducted at a temperature above 80° C.

18. The process of claim 2, wherein said heat treatment step is conducted at a temperature above 90° C.

19. The process of claim 2, wherein said aqueous polymer coating composition comprises at least one of ethylcellulose, methacrylate copolymers, acrylate copolymers, water insoluble cellulosics, cellulose acetate phthalate, Eudragit® polymer, Surelease® polymer latex, cellulose acetate trimellaite, polyvinyl acetate phthalate, Sureteric® polymer latex, hydroxypropylmethylcellulose phthalate, hydroxypropylmethylcellulose acetate succinate, polylactide or silicone elastomer latex.

20. The process of claim 2, where humidity in step (i) is maintained by humidification of the process air.

21. The process of claim 2, where high humidity in step (i) is maintained by spraying an aqueous solution into a coating chamber comprising the substrate.

22. The process of claim 2, where high humidity in step (i) is maintained by diluting the aqueous polymer coating composition with an aqueous solution.

23. The process of claim 2, wherein said aqueous coating composition is present in an amount less than that used for said aqueous coating composition on a substrate under low humidity coating and low humidity curing conditions.

24. The process of claim 2, wherein said aqueous coating composition is present in an amount less than 8% by weight of said substrate.

25. The process of claim 2, wherein said aqueous coating composition is present in an amount less than 6% by weight of said substrate.

26. The process of claim 2, wherein said aqueous coating composition is present in an amount less than 4% by weight of said substrate.

27. The process of claim 2, wherein said aqueous coating composition is present in an amount less than 2% by weight of said substrate.

28. The process of claim 2, wherein said aqueous coating composition is present in an amount less than 1.5% by weight of said substrate.

29. The process of claim 2, wherein said aqueous coating composition is present in an amount less than 1% by weight of said substrate.

30. The process of claim 2, wherein said aqueous coating composition is present in an amount less than 0.5% by weight of said substrate.

31. The process of claim 2, wherein said substrate is selected from the group consisting of a pellet, a tablet, a soft capsule, a hard capsule, a powder, a granules, a bead, a film and a film-enrobed dosage form.

32. A coated substrate prepared by the process of claim 2.

33. The product of claim 32, wherein said coated substrate has superior barrier properties to a coated substrate of the same coating composition and substrate prepared under low humidity coating and low humidity curing conditions.

34. The product of claim 32, wherein said coated substrate has superior stability of release profile over a period of up to three years under normal storage conditions to a coated substrate of the same coating composition and substrate prepared under low humidity coating and low humidity curing conditions.

35. The product of claim 32, wherein said coated substrate has a lower diffusivity as compared to a coated substrate of the same coating composition and substrate prepared under low humidity coating and low humidity curing conditions.

36. The process of claim 2, wherein said high humidity condition is created by an aqueous coating composition having a low solids content.