System and method for enhanced electrostatic deposition and surface coatings

• US 9,687,864 B2
• Filed: 06/20/2014
• Issued: 06/27/2017
• Est. Priority Date: 03/26/2010
• Status: Active Grant

• Current Assignee: Micell Medtech Incorporated
• Original Assignee: Battelle Memorial Institute
• Inventors: McClain, James B., Matson, Dean W., Taylor, C. Douglas, Fulton, John L., Deverman, George S., Yonker, Clement R., Crowley, Joseph M.
• Primary Examiner(s): TADESSE, YEWEBDAR T
• Application Number:
  US14/310,960
• Publication Number:
  US 20150040827A1
• Time in Patent Office: 1,103 Days
• Field of Search: 118620-640, 239690-708, 427458, 427475-486
• CPC Class Codes: B05B 5/032 for spraying particulate materials
• CPC Class Codes: B05D 1/025 using gas close to its critical state
• CPC Class Codes: B05D 1/04 involving the use of an electrostatic field B05D1/025 and B05D1/14 take precedence
• CPC Class Codes: B05D 3/0486 Operating the coating or treatment in a controlled atmosphere
• CPC Class Codes: Y10T 428/24372 Particulate matter
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/31504 Composite [nonstructural laminate]
• CPC Class Codes: Y10T 428/31507 Of polycarbonate
• CPC Class Codes: Y10T 428/31511 Of epoxy ether
• CPC Class Codes: Y10T 428/31544 Addition polymer is perhalogenated
• CPC Class Codes: Y10T 428/31551 Of polyamidoester [polyurethane, polyisocyanate, polycarbamate, etc.]
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane
• CPC Class Codes: Y10T 428/31725 Of polyamide
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]
• CPC Class Codes: Y10T 428/31855 Of addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31931 Polyene monomer-containing
• CPC Class Codes: Y10T 428/31935 Ester, halide or nitrile of addition polymer
• CPC Class Codes: Y10T 428/31938 Polymer of monoethylenically unsaturated hydrocarbon

Abstract

This disclosure describes the application of a supplemental corona source to provide surface charge on submicrometer particles to enhance collection efficiency and micro-structural density during electrostatic collection.

Claims

1. A system for electrostatic deposition of particles upon a charged substrate to form a coating on a surface of said substrate, the system comprising:

a vessel;

an expansion nozzle that releases coating particles having a first average electric potential suspended in a gaseous phase from a near-critical or supercritical fluid that is expanded through said nozzle;

at a first location into said vessel;

and

an auxiliary emitter that generates a stream of charged ions having a second average electric potential in an inert carrier gas at a second location into said vessel, the second location being separated from the first location, wherein said auxiliary emitter comprises an electrode having a tapered end that extends into a gas channel that conducts said stream of charged ions in said inert carrier gas toward said charged coating particles;

whereby said coating particles interact with said charged ions and said carrier gas within said vessel to enhance a charge differential between said coating particles and said substrate.

2. The system of claim 1, wherein the coating particles have a first velocity upon release of the coating particles from the expansion nozzle that is less than a second velocity of the coating particles when said coating particles impact said substrate.

3. The system of claim 2, wherein the second velocity is in the range from about 0.1 cm/sec to about 100 cm/sec.

4. The system of claim 1, wherein attraction of the coating particles to the substrate is increased as compared to attraction of the coating particles to the substrate in a system without the auxiliary emitter.

5. The system of claim 1, wherein the first average electric potential is different than the second average electric potential.

6. The system of claim 1, wherein an absolute value of the first average electric potential is less than an absolute value of the second average electric potential, and wherein a polarity of the charged ions is the same as a polarity of the coating particles.

7. The system of claim 1, wherein said auxiliary emitter further comprises a capture electrode.

8. The system of claim 1, wherein said substrate is positioned in a circumvolving orientation around said expansion nozzle.

9. The system of claim 1, wherein said substrate comprises a conductive material.

10. The system of claim 1, wherein said substrate comprises a semi-conductive material.

11. The system of claim 1, wherein said substrate comprises a polymeric material.

12. The system of claim 1, wherein said charged ions at said second electric potential are a positive corona or a negative corona positioned between the expansion nozzle and said substrate.

13. The system of claim 1, wherein said charged ions at said second electric potential are a positive corona or a negative corona positioned between the auxiliary emitter and said substrate.

14. The system of claim 1, wherein said coating particles comprises at least one of:

polylactic acid (PLA);

poly(lactic-co-glycolic acid) (PLGA);

polycaprolactone (poly(e-caprolactone)) (PCL), polyglycolide (PG) or (PGA), poly-3-hydroxybutyrate;

LPLA poly(l-lactide), DLPLA poly(dl-lactide), PDO poly(dioxolane), PGA-TMC, 85/15 DLPLG p(dl-lactide-co-glycolide), 75/25 DLPLG, 65/35 DLPLG, 50/50 DLPLG, TMC poly(trimethylcarbonate), p(CPP;

SA) poly(1,3-bis-p-(carboxyphenoxy)propane-co-sebacic acid) and blends, combinations, homopolymers, condensation polymers, alternating, block, dendritic, crosslinked, or copolymers thereof.

15. The system of claim 1, wherein said coating particles comprise at least one of:

polyester, aliphatic polyester, polyanhydride, polyethylene, polyorthoester, polyphosphazene, polyurethane, polycarbonate urethane, aliphatic polycarbonate, silicone, a silicone containing polymer, polyolefin, polyamide, polycaprolactam, polyamide, polyvinyl alcohol, acrylic polymer, acrylate, polystyrene, epoxy, polyethers, celluiosics, expanded polytetrafluoroethylene, phosphorylcholine, polyethyleneyerphthalate, polymethylmethavrylate, poly(ethylmethacrylate/n-butylmethacrylate), parylene C, polyethylene-co-vinyl acetate, polyalkyl methacrylates, polyalkylene-co-vinyl acetate, polyalkylene, polyalkyl siloxanes, polyhydroxyalkanoate, polyfluoroalkoxyphasphazine, poly(styrene-b-isobutylene-b-styrene), poly-butyl methacrylate, poly-byta-diene, and blends, combinations, homopolymers, condensation polymers, alternating, block, dendritic, crosslinked, or copolymers thereof.

16. The system of claim 1, wherein said coating particles have a size between about 0.01 micrometers and about 10 micrometers.

17. The system of claim 1, wherein the coating has a density on said surface in the range from about 1 volume % to about 60 volume %.

18. The system of claim 1, wherein the coating is a multilayer coating.

19. The system of claim 1, wherein said substrate is a medical implant.

20. The system of claim 1, wherein said substrate is an interventional device.

21. The system of claim 1, wherein said substrate is a diagnostic device.

22. The system of claim 1, wherein said substrate is a surgical tool.

23. The system of claim 1, wherein said substrate is a stent.

24. The system of claim 1, wherein the coating is non-dendritic as compared to a baseline average coating thickness.

25. The system of claim 24, wherein no coating extends more than 0.5 microns from the baseline average coating thickness.

26. The system of claim 24, wherein no coating extends more than 1 micron from the baseline average coating thickness.

27. The system of claim 1, wherein the coating is non-dendritic such that there is no surface irregularity of the coating greater than 0.5 microns.

28. The system of claim 1, wherein the coating is non-dendritic such that there is no surface irregularity of the coating greater than 1 micron.

29. The system of claim 1, wherein the coating is non-dendritic such that there is no surface irregularity of the coating greater than 2 microns following sintering of the coated substrate.

30. The system of claim 1, wherein the coating is non-dendritic such that there is no surface irregularity of the coating greater than 3 microns following sintering of the coated substrate.

31. A system for electrostatic deposition of particles upon a charged substrate to form a coating on a surface of a substrate, the system comprising:

a vessel;

an expansion nozzle that releases coating particles having a first average electric potential suspended in a gaseous phase from a near-critical or supercritical fluid that is expanded through said nozzle;

at a first location into said vessel;

and

an auxiliary emitter that generates a stream of charged ions having a second average electric potential in an inert carrier gas at a second location into said vessel, the second location being separated from the first location, wherein said auxiliary emitter comprises a metal rod with a tapered tip and a delivery orifice;

whereby said coating particles interact with said charged ions and said carrier gas within a said vessel to enhance a potential differential between said coating particles and said substrate.