Electrospinning of PTFE

• US 9,856,588 B2
• Filed: 03/03/2015
• Issued: 01/02/2018
• Est. Priority Date: 01/16/2009
• Status: Active Grant

• Current Assignee: Zeus Co. LLC
• Original Assignee: Zeus Industrial Products, Inc.
• Inventors: Anneaux, Bruce L., Ballard, Robert L., Garner, David P.
• Primary Examiner(s): Kaucher, Mark
• Assistant Examiner(s): HU, HENRY S
• Application Number:
  US14/636,274
• Publication Number:
  US 20150183940A1
• Time in Patent Office: 1,036 Days
• Field of Search: 524544, 523201
• CPC Class Codes: B05D 1/007 using an electrostatic field B05D1/02 - B05D1/16 take precedence
• CPC Class Codes: B29B 11/06 by moulding the material
• CPC Class Codes: B29B 13/023 Half-products, e.g. films, plates
• CPC Class Codes: B29C 55/04 uniaxial, e.g. oblique
• CPC Class Codes: B29K 2027/18 PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: B29K 2105/0094 having particular viscosity
• CPC Class Codes: B29K 2995/0063 Density
• CPC Class Codes: B29K 2995/0077 Yield strength; Tensile strength
• CPC Class Codes: B29L 2031/755 Membranes, diaphragms
• CPC Class Codes: B32B 1/08 Tubular products
• CPC Class Codes: B32B 15/085 comprising polyolefins
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 5/022 Non-woven fabric
• CPC Class Codes: B32B 9/005 comprising one layer of ceramic material, e.g. porcelain, ceramic tile layered products with at least two ceramic layers composed mainly of ceramic B32B18/00
• CPC Class Codes: C08F 114/26 Tetrafluoroethene
• CPC Class Codes: C08J 2327/18 Homopolymers or copolymers of tetrafluoroethylene
• CPC Class Codes: C08J 2471/02 Polyalkylene oxides
• CPC Class Codes: C08J 3/005 Processes for mixing polymers
• CPC Class Codes: C08J 3/05 from solid polymers
• CPC Class Codes: C08J 9/232 by sintering expandable particles
• CPC Class Codes: D01D 10/02 : Heat treatment heating for finishing D02J13/00
• CPC Class Codes: D01D 5/0007 : Electro-spinning non-woven fabrics produced by electro-spinning D04H1/728
• CPC Class Codes: D01D 5/003 : the material being a polymer solution or dispersion D01D5/0053 takes precedence
• CPC Class Codes: D01D 5/0038 : the fibre formed by solvent evaporation, i.e. dry electro-spinning
• CPC Class Codes: D01F 6/12 : from polymers of fluorinated hydrocarbons
• CPC Class Codes: D01F 6/48 : of polymers of halogenated hydrocarbons
• CPC Class Codes: D04H 1/413 : containing granules other than absorbent substances
• CPC Class Codes: D04H 1/42 : characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
• CPC Class Codes: D04H 1/4318 : Fluorine series
• CPC Class Codes: D04H 1/4326 : Condensation or reaction polymers
• CPC Class Codes: D04H 1/54 : by welding together the fibres, e.g. by partially melting or dissolving in combination with needling D04H1/485
• CPC Class Codes: D04H 1/728 : by electro-spinning electro-spinning methods and apparatus D01D5/0007
• CPC Class Codes: D04H 1/74 : the fibres being orientated, e.g. in parallel (anisotropic fleeces)
• CPC Class Codes: D04H 3/02 : characterised by the method of forming fleeces or layers, e.g. reorientation of yarns or filaments
• CPC Class Codes: D06N 7/00 : Flexible sheet materials not otherwise provided for, e.g. textile threads, filaments, yarns or tow, glued on macromolecular material paper-based or board-based structures for surface covering D21H27/20
• CPC Class Codes: D10B 2321/042 : polymers of fluorinated hydrocarbons, e.g. polytetrafluoroethene [PTFE]
• CPC Class Codes: Y10T 428/1314 : Contains fabric, fiber particle, or filament made of glass, ceramic, or sintered, fused, fired, or calcined metal oxide, or metal carbide or other inorganic compound [e.g., fiber glass, mineral fiber, sand, etc.]
• CPC Class Codes: Y10T 428/1355 : Elemental metal containing [e.g., substrate, foil, film, coating, etc.]
• CPC Class Codes: Y10T 428/1362 : Textile, fabric, cloth, or pile containing [e.g., web, net, woven, knitted, mesh, nonwoven, matted, etc.]
• CPC Class Codes: Y10T 442/60 : Nonwoven fabric [i.e., nonwoven strand or fiber material]
• CPC Class Codes: Y10T 442/656 : Preformed metallic film or foil or sheet [film or foil or sheet had structural integrity prior to association with the nonwoven fabric]
• CPC Class Codes: Y10T 442/674 : Nonwoven fabric with a preformed polymeric film or sheet
• CPC Class Codes: Y10T 442/681 : Spun-bonded nonwoven fabric

Abstract

An improved process for forming a PTFE mat is described. The process includes providing a dispersion with PTFE, a fiberizing polymer and a solvent wherein said dispersion has a viscosity of at least 50,000 cP. An apparatus is provided which comprises a charge source and a target a distance from the charge source. A voltage source is provided which creates a first charge at the charge source and an opposing charge at the target. The dispersion is electrostatically charged by contact with the charge source. The electrostatically charged dispersion is collected on the target to form a mat precursor which is heated to remove the solvent and the fiberizing polymer thereby forming the PTFE mat.

Claims

1. A method of preparing a spinning dispersion, comprising:

adding a fiberizing polymer to a polytetrafluoroethylene (PTFE) aqueous dispersion to form a PTFE/Polymer dispersion, wherein the PTFE/Polymer dispersion comprises at least 1% by weight of the fiberizing polymer in relation to weight of the PTFE/Polymer dispersion to no more than 10% by weight of the fiberizing polymer in relation to weight of the PTFE/Polymer dispersion, and wherein the PTFE/Polymer dispersion has a viscosity of at least 50,000 cP.

2. The method of claim 1, wherein the PTFE/Polymer dispersion comprises 50-80 wt % PTFE solids.

3. The method of claim 2, wherein the PTFE/Polymer dispersion comprises 59-61 wt % PTFE solids.

4. The method of claim 1, wherein the PTFE/Polymer dispersion comprises a weight ratio of fiberizing polymer to PTFE/Polymer dispersion of at least 3.0 to no more than 5.5.

5. The method of claim 1, wherein the fiberizing polymer comprises polyethylene oxide (PEO), the PTFE/Polymer dispersion comprises a PTFE/PEO dispersion, and wherein the ratio of PEO to PTFE corresponds to a ratio in the range of 0.03 to 0.06 grams of PEO per ml of 60 wt % PTFE dispersion.

6. The method of claim 5, wherein the ratio of PEO to PTFE corresponds to a ratio of between 0.032 and 0.052 grams of PEO per ml of 60 wt % PTFE dispersion.

7. The method of claim 6, wherein the ratio of PEO to PTFE corresponds to a ratio of about 0.048 grams of PEO per ml of 60 wt % PTFE dispersion.

8. The method of claim 5, further comprising mixing the PTFE/PEO dispersion in a jar roller turning at a constant rate.

9. The method of claim 8, wherein mixing the PTFE/PEO dispersion comprises mixing in a jar roller turning at a constant rate for at least 24 hours.

10. The method of claim 5, further comprising filtering PTFE/PEO dispersion to remove clumps.

11. The method of claim 5, further comprising allowing the PTFE/PEO dispersion to homogenize.

12. The method of claim 1, wherein a molecular weight of the fiberizing polymer is 200,000 to 4,000,000 Mw.

13. The method of claim 1, wherein the spinning dispersion is spun to create one or more fibers, the one or more fibers having a diameter of about 0.8 microns.

14. The method of claim 1, wherein PTFE particles dispersed in the spinning dispersion have a particle size of no more than 0.8 microns.

15. The method of claim 1, wherein PTFE particles dispersed in the spinning dispersion have a particle size of at least 0.1 microns.

16. The method of claim 1, wherein PTFE particles dispersed in the spinning dispersion have a particle size in a range of 0.2 microns to 0.6 microns.