Corrosion-resistant magnetic article

Patent metadata

Field	Value
Publication number	US-9775974-B2
Application number	US-201514603027-A
Country	US
Kind code	B2
Filing date	Jan 22, 2015
Priority date	Jan 22, 2015
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

A magnetic article with a corrosion resistant barrier formed from a poly(tetrafluoro-p-xylene) conformal coating or from a parylene conformal coating having a melting point of at least about 430° C. and a moisture vapor transmission less than about 0.5 g-mm/m 2 /day at 90% RH and 37° C., the conformal coating being covered with a polysulfone thermoplastic overlayer.

First claim

The invention claimed is:

1. A magnetic article comprising an NdFeB magnet having thereon a substantially continuous corrosion resistant barrier comprising a fluorinated parylene conformal coating covered with a polysulfone thermoplastic overlayer, wherein the polysulfone melting point is also less than the magnet Curie temperature T c .

2. A magnetic article according to claim 1 wherein the magnet has a Maximum Energy Product BH max of at least 28 Mega Gauss Oersteds, an Intrinsic Coercive Force H ci of at least 10 kiloOersteads and a Curie Temperature T c of at least 300° C.

3. A magnetic article according to claim 1 wherein the magnet has a Maximum Energy Product BH max of at least 32 Mega Gauss Oersteds, an Intrinsic Coercive Force H ci of at least 35 kiloOersteads and a Curie Temperature T c of at least 310° C.

4. A magnetic article according to claim 1 wherein the magnet comprises a bar, rod, ring, partial ring or plate.

5. A magnetic article according to claim 1 wherein the fluorinated parylene has fluoroaliphatic groups.

6. A magnetic article according to claim 1 wherein the conformal coating comprises poly(tetrafluoro-p-xylene).

7. A magnetic article according to claim 1 wherein the fluorinated parylene has fluoroaromatic groups.

8. A magnetic article according to claim 1 wherein the conformal coating comprises parylene VT-4.

9. A magnetic article according to claim 1 wherein the conformal coating has a thickness of 2 to 100 μm.

10. A magnetic article according to claim 1 wherein the overlayer comprises polyethersulfone.

11. A magnetic article according to claim 1 wherein the overlayer comprises sulfonated polyethersulfone or polyphenylsulfone.

12. A magnetic article according to claim 1 wherein the overlayer has an average thickness of 0.5 to 10 mm.

13. A magnetic article according to claim 1 wherein the overlayer has a variable thickness.

14. A magnetic article according to claim 1 wherein the overlayer is an overmolding and is a layer made by injection molding.

15. A magnetic article according to claim 1 wherein the polysulfone melting point is less than the parylene melting point.

16. A magnetic article according to claim 1 wherein the conformal coating has a thickness less than 0.5 mm and the overlayer has an average thickness greater than 0.5 mm.

17. A magnetic article according to claim 1 wherein the magnet or overlayer has a recess or protrusion.

18. A magnetic article according to claim 17 wherein the recess or protrusion comprises a groove, notch, detent, aperture, spline, tab, stop, step, sealing surface, pivot point, axle, bearing surface, indicator to depict direction of fluid flow or magnetization, spring retaining collar, valve or valve actuator.

19. A magnetic article according to claim 1 wherein the magnet does not exhibit visible corrosion after 5 days immersion in 37° C. normal saline solution.

20. A magnetic article according to claim 1 wherein the magnet retains its full magnetic strength without exhibiting visible corrosion after 20 days immersion in 87° C. normal saline solution.

21. A magnetic article comprising an NdFeB magnet having thereon a substantially continuous corrosion resistant barrier comprising a parylene conformal coating having a melting point of at least about 430° C. and a moisture vapor transmission less than about 0.5 g-mm/m 2 /day at 90% RH and 37° C., the parylene conformal coating being covered with a polysulfone thermoplastic overlayer, wherein the polysulfone melting point is also less than the magnet Curie temperature T c .

22. A magnetic article according to claim 21 wherein the conformal coating has a moisture vapor transmission less than about 0.4 g-mm/m 2 /day at 90% RH and 37° C.

23. A magnetic article according to claim 21 wherein the conformal coating has a moisture vapor transmission less than about 0.3 g-mm/m 2 /day at 90% RH and 37° C.

24. A method for making a coated magnetic article, which method comprises vapor depositing upon an NdFeB magnet a layer or layers of a poly(tetrafluoro-p-xylene) conformal coating, and applying molten polysulfone over the poly(tetrafluoro-p-xylene) conformal coating, to provide a substantially continuous corrosion resistant barrier over the magnet, wherein the polysulfone melting point is also less than the magnet Curie temperature T c .

25. A method for making a coated magnetic article, which method comprises vapor depositing upon an NdFeB magnet a layer or layers of a parylene conformal coating having a melting point of at least about 430° C. and a moisture vapor transmission less than about 0.5 g-mm/m 2 /day at 90% RH and 37° C., and applying molten polysulfone over the parylene conformal coating, to provide a substantially continuous corrosion resistant barrier over the magnet, wherein the polysulfone melting point is also less than the magnet Curie temperature T c .

26. An implantable medical device containing a coated magnetic article comprising an NdFeB magnet having thereon a substantially continuous corrosion resistant barrier comprising a poly(tetrafluoro-p-xylene) conformal coating covered with a polysulfone thermoplastic overlayer, wherein the polysulfone melting point is also less than the magnet Curie temperature T c .

27. An implantable medical device containing a coated magnetic article comprising an NdFeB magnet having thereon a substantially continuous corrosion resistant barrier comprising a parylene conformal coating having a melting point of at least about 430° C. and a moisture vapor transmission less than about 0.5 g-mm/m 2 /day at 90% RH and 37° C., covered with a polysulfone thermoplastic overlayer, wherein the polysulfone melting point is also less than the magnet Curie temperature T c .

Assignees

• Medtronic Xomed Inc

Inventors

• Leung Chun Man Alan
• Bertrand William Jeffrey
• Amery Drew Powell
• Speckman Lori C
• Sierocuk Thomas J

Classifications

• H01F41/026 Primary

  protecting methods against environmental influences, e.g. oxygen, by surface treatment (magnetic particles with skin H01F1/061, H01F1/09, H01F1/24, H01F1/33 and G11B5/706) · CPC title

• A61L31/14

  Materials characterised by their function or physical properties {, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials} · CPC title

• A61M2207/00

  Methods of manufacture, assembly or production · CPC title

• A61L2420/02

  Methods for coating medical devices · CPC title

• A61L31/028

  Other inorganic materials not covered by A61L31/022 - A61L31/026 · CPC title