Method and system of purifying polymers for use with implantable medical devices

• US 7,645,474 B1
• Filed: 07/31/2003
• Issued: 01/12/2010
• Est. Priority Date: 07/31/2003
• Status: Expired due to Fees

• Current Assignee: Advanced Cardiovascular Systems Incorporated (Abbott Laboratories)
• Original Assignee: Advanced Cardiovascular Systems Incorporated (Abbott Laboratories)
• Inventors: Tang, Fuh-Wei, Pathak, Jaya
• Primary Examiner(s): Meeks; Timothy H
• Assistant Examiner(s): LIN, JAMES
• Application Number:
  US10/631,228
• Time in Patent Office: 2,357 Days
• Field of Search: 427/2.1, 427/592
• US Class Current: 427/2.1
• CPC Class Codes: A61L 31/048 obtained by reactions only involving carbon-to-carbon unsaturated bonds A61L31/041 takes precedence
• CPC Class Codes: C08L 27/16 Homopolymers or copolymers or vinylidene fluoride
• CPC Class Codes: C08L 31/06 Homopolymers or copolymers of esters of polycarboxylic acids

Abstract

A method and system for purifying polymers to use with medical devices, particularly for a drug eluting stent, is described.

Claims

1. A method of manufacturing an implantable medical device, comprising:

purifying a polymer by;

introducing the polymer into an extruder;

introducing a fluid into the extruder;

mixing the fluid with the polymer;

removing at least a volume of the fluid from the extruder such that an impurity is completely or at least partially removed with the fluid; and

collecting the polymer after removal of the impurity; and

coating an implantable medical device with the purified polymer, or fabricating the implantable medical device with the purified polymer;

wherein the fluid is of a type to physically entrap the impurity without dissolving the impurity or the fluid is of a type to dissolve the impurity.

2. The method of claim 1, wherein the extruder is selected from the group consisting of a single screw extruder, an intermeshing co-rotating extruder and a counter-rotating twin-screw extruder.

3. The method of claim 1, wherein the polymer is exposed to a temperature equal to or greater than the melting temperature of the polymer.

4. The method of claim 1, further comprising heating the polymer to a temperature equal to or greater than the melting temperature of the polymer.

5. The method of claim 1, the method further comprising introducing a second fluid into the extruder, and mixing the second fluid with the polymer and removing the second fluid and an impurity from the extruder.

6. The method of claim 1, wherein the polymer is selected from the group consisting of an ethylene vinyl alcohol copolymer, poly(butyl methacrylate), poly(vinylidene fluoride-co-hexafluororpropene), polyvinylidene fluoride, poly(L-lactic acid), poly(caprolactone), an ethylene-vinyl acetate copolymer and polyethylene glycol.

7. The method of claim 1, wherein the fluid is selected from the group consisting of water, isopropyl alcohol, methanol, FLUX REMOVER AMS, acetone, ethanol, dimethyl acetamide, acetonitrile, dimethyl formamide, cyclohexane, dimethyl sulfoxide, and combinations thereof.

8. The method of claim 1, further comprising exposing the fluid to a temperature equal to or greater than the boiling temperature of the fluid at ambient pressure prior to removing the fluid from the extruder.

9. A method of manufacturing a coating for an implantable medical device, comprising:

(a) purifying a thermoplastic polymer, the purifying including introducing the polymer into an extruder,

introducing a fluid into the extruder,

mixing the fluid with the polymer,

removing at least a portion of the fluid and an impurity from the extruder, and collecting the polymer after removal of the impurity; and

(b) applying a composition to an implantable medical device, the composition including the purified polymer, a solvent and optionally a therapeutic agent;

wherein the fluid is of a type to physically entrap the impurity without dissolving the impurity or the fluid is of a type to dissolve the impurity.

10. The method of claim 9, the method further comprising exposing the polymer to a temperature equal to or greater than the melting temperature of the polymer while the polymer is in the extruder.

11. The method of claim 9, wherein the polymer is selected from the group consisting of an ethylene vinyl alcohol copolymer, poly(butyl methacrylate), poly(vinylidene fluoride-co-hexafluororpropene), polyvinylidene fluoride, poly(L-lactic acid), poly(caprolactone), an ethylene-vinyl acetate copolymer and polyethylene glycol.

12. The method of claim 9, wherein the fluid is selected from the group consisting of water, isopropyl alcohol, methanol, FLUX REMOVER AMS, acetone, ethanol, dimethyl acetamide, acetonitrile, dimethyl formamide, cyclohexane, dimethyl sulfoxide, and combinations thereof.

13. The method of claim 9, wherein the purifying further includes introducing a second fluid into the extruder, and mixing the second fluid with the polymer and removing the second fluid

and the impurity from the extruder, wherein the second fluid is of a type that dissolves the impurity and the second fluid is not the same as the first fluid.

14. The method of claim 9, further comprising exposing the fluid to a temperature equal to or greater than the boiling temperature of the fluid at ambient pressure prior to removing the fluid.

15. A method of manufacturing an implantable medical device, comprising:

purifying a polymer by;

introducing the polymer into an extruder;

introducing a fluid into the extruder, the fluid selected from the group consisting of FLUX REMOVER AMS, dimethyl acetamide, dimethyl formamide, dimethyl sulfoxide, and combinations thereof;

mixing the fluid with the polymer;

removing at least a volume of the fluid from the extruder such that an impurity is completely or at least partially removed with the fluid; and

collecting the polymer after removal of the impurity; and

coating an implantable medical device with the purified polymer.

16. The method of claim 15, further comprising exposing the fluid to a temperature equal to or greater than the boiling temperature of the fluid at ambient pressure after the fluid has removed the impurity.

17. The method of claim 15, wherein the extruder is selected from the group consisting of a single screw extruder, an intermeshing co-rotating extruder and a counter-rotating twin-screw extruder.

18. The method of claim 15, wherein the polymer is exposed to a temperature equal to or greater than the melting temperature of the polymer.

19. The method of claim 15, further comprising heating the polymer to a temperature equal to or greater than the melting temperature of the polymer.

20. The method of claim 15, wherein the fluid is of a type to physically entrap the impurity without dissolving the impurity.

21. The method of claim 15, the method further comprising introducing a second fluid into the extruder, and mixing the second fluid with the polymer and removing the second fluid and an impurity from the extruder.

22. A method of manufacturing an implantable medical device, comprising:

purifying a polymer by;

introducing the polymer into an extruder, the polymer having an impurity;

introducing a first fluid into the extruder, the first fluid acting as a solvent for the impurity;

mixing the first fluid with the polymer;

removing at least a volume of the first fluid from the extruder such that the impurity is at least partially removed with the first fluid;

introducing a second fluid into the extruder, the second fluid acting as a non-solvent for the impurity;

mixing the second fluid with the polymer;

removing at least a volume of the second fluid from the extruder such that the impurity is at least partially removed with the second fluid; and

collecting the polymer after removal of the impurity; and

coating an implantable medical device with the collected polymer, or fabricating the implantable medical device with the collected polymer, wherein the second fluid is not the same as the first fluid.

23. The method of claim 22, wherein after the first fluid has removed the impurity, exposing the first fluid to a temperature equal to or greater than the boiling temperature of the first fluid at ambient pressure prior to removing the first fluid from the extruder.

24. The method of claim 22, wherein after the second fluid has removed the impurity, exposing the second fluid to a temperature equal to or greater than the boiling temperature of the second fluid at ambient pressure prior to removing the second fluid from the extruder.

25. The method of claim 22, wherein the polymer is poly(vinylidene fluoride-co-hexafluororpropene) or poly(butyl methacrylate).