Method of manufacturing a composite filter media

• US 7,927,540 B2
• Filed: 08/01/2008
• Issued: 04/19/2011
• Est. Priority Date: 03/05/2007
• Status: Active Grant

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.), Parker Intangibles LLC (Parker-Hannifin Corporation)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.), BHA Group Incorporated (GE Aerospace)
• Inventors: Jones, David Charles, Lim, Hyun Sung, Clements, Jack T., Smithies, Alan
• Primary Examiner(s): Del Sole; Joseph S
• Assistant Examiner(s): SANDERS, JAMES M
• Application Number:
  US12/184,634
• Publication Number:
  US 20080315464A1
• Time in Patent Office: 991 Days
• Field of Search: 264/172.12, 264/DIG.48, 264/454, 264/103, 264/173.1
• US Class Current: 264/454
• CPC Class Codes: B01D 2239/0216 Bicomponent or multicomponent fibres
• CPC Class Codes: B01D 2239/0225 Side-by-side
• CPC Class Codes: B01D 2239/025 comprising nanofibres apparatus incorporating such gas filtering material see B01D46/546
• CPC Class Codes: B01D 2239/064 The fibres being mixed
• CPC Class Codes: B01D 2239/065 More than one layer present in the filtering material apparatus incorporating such gas filtering material B01D2275/10
• CPC Class Codes: B01D 2275/10 Multiple layers
• CPC Class Codes: B01D 2323/39 Electrospinning
• CPC Class Codes: B01D 2325/20 Specific permeability or cut-off range
• CPC Class Codes: B01D 2325/32 Melting point or glass-transition temperatures
• CPC Class Codes: B01D 39/1623 of synthetic origin
• CPC Class Codes: B01D 39/163 sintered or bonded
• CPC Class Codes: B01D 46/0001 Making filtering elements
• CPC Class Codes: B01D 46/521 using folded, pleated material
• CPC Class Codes: B01D 46/546 using nano- or microfibres
• CPC Class Codes: B01D 63/065 on the outer surface thereof
• CPC Class Codes: B01D 63/067 with pleated membranes
• CPC Class Codes: B01D 69/02 characterised by their properties
• CPC Class Codes: B01D 69/10 Supported membranes; Membrane supports
• CPC Class Codes: B01D 71/06 Organic material
• CPC Class Codes: D01D 5/0069 characterised by the spinning section, e.g. capillary tube, protrusion or pin
• CPC Class Codes: D01D 5/0084 : Coating by electro-spinning, i.e. the electro-spun fibres are not removed from the collecting device but remain integral with it, e.g. coating of prostheses
• CPC Class Codes: D01D 5/0985 : by means of a flowing gas (e.g. melt-blowing)
• CPC Class Codes: D04H 1/4374 : using different kinds of webs, e.g. by layering webs
• CPC Class Codes: D04H 1/559 : the fibres being within layered webs
• CPC Class Codes: D04H 1/728 : by electro-spinning electro-spinning methods and apparatus D01D5/0007
• CPC Class Codes: D04H 3/14 : with bonds between thermoplastic yarns or filaments produced by welding

Abstract

A method of making a composite filter media includes, in an exemplary embodiment, forming a nonwoven fabric mat that includes a plurality of synthetic fibers by a spunbond process, and calendaring the nonwoven fabric mat with embossing calendar rolls to form a bond area pattern comprising a plurality of substantially parallel discontinuous lines of bond area to bond the synthetic fibers together to form a nonwoven fabric, the nonwoven fabric having a minimum filtration efficiency of about 50%, measured in accordance with ASHRAE 52.2-1999 test procedure. The method also includes applying a nanofiber layer by electro-blown spinning a polymer solution to form a plurality of nanofibers on at least one side of the nonwoven fabric mat to form the composite filter media, the composite filter media having a minimum filtration efficiency of about 75%, measured in accordance with ASHRAE 52.2-1999 test procedure.

Claims

1. A method of making a composite filter media, said method comprising:

forming a nonwoven fabric mat comprising a plurality of synthetic bicomponent fibers by a spunbond process, the plurality of bicomponent fibers comprising a core material and a sheath material, the sheath material having a lower melting point than the core material;

calendering the nonwoven fabric mat with heated embossing calender rolls having an embossing pattern, to melt the sheath material to bond the bicomponent fibers at contact areas of the embossing pattern the embossing pattern forming a bond area pattern in the nonwoven fabric mat having a bond area of the spunbond fibers of about 10% to about 16% of an area of the nonwoven fabric mat, said bond area pattern comprising a plurality of substantially parallel discontinuous lines of bond area to bond the synthetic fibers together to form a nonwoven fabric, the nonwoven fabric having a minimum filtration efficiency of about 50%, measured in accordance with ASHRAE 52.2-1999 test procedure; and

applying a nanofiber layer by electro-blown spinning a polymer solution to form a plurality of nanofibers on at least one side of the nonwoven fabric to form the composite filter media, the composite filter media having a minimum filtration efficiency of about 75%, measured in accordance with ASHRAE 52.2-1999 test procedure.

2. A method in accordance with claim 1, wherein the nonwoven fabric and the nanofiber layer in combination are substantially electrically neutral.

3. A method in accordance with claim 1, wherein applying a nanofiber layer comprises applying a nanofiber layer by an electro-blown spinning process, an electrospinning process, a centrifugal spinning process, or a melt blowing process.

4. A method in accordance with claim 1, wherein the core material comprises at least one of polyester, polyamide, polyolefin, thermoplastic polyurethane, polyetherimide, polyphenyl ether, polyphenylene sulfide, polysulfone, and aramid.

5. A method in accordance with claim 1, wherein calendering the nonwoven fabric mat comprises calendering the nonwoven fabric mat from a nonwoven fabric having a basis weight of about 100 g/m² to about 300 g/m².

6. A method in accordance with claim 1, wherein calendering the nonwoven fabric mat comprises calendering the nonwoven fabric mat to form a nonwoven fabric having a basis weight of about 150 g/m² to about 220 g/m².

7. A method in accordance with claim 1, wherein applying a nanofiber layer comprises applying a plurality of nanofibers having an average diameter of about 500 nm or less to form the nanofiber layer having a basis weight of about 0.6 g/m² to about 20 g/m².

8. A method in accordance with claim 1, wherein applying a nanofiber layer comprises applying a plurality of nanofibers having an average diameter of about 500 nm or less to form the nanofiber layer having a basis weight of about 1.5 g/m² to about 2.5 g/m².

9. A method in accordance with claim 1, wherein forming a nonwoven fabric mat comprising a plurality of synthetic fibers by a spunbond process comprises forming a nonwoven fabric mat comprising a plurality of synthetic bicomponent fibers having an average diameter of about 12 to about 25 microns.

10. A method in accordance with claim 1, wherein the nonwoven fabric has a resistance less than about 2.5 mm of water, measured in accordance with EN-1822 (1998), and the composite filter media has a resistance less than about 4.0 mm of water, measured in accordance with EN-1822 (1998).

11. A method in accordance with claim 10, wherein a quality factor Q_f of the composite filter media is greater than about 450.

12. A method in accordance with claim 10, wherein a quality factor Q_f of the composite filter media is greater than about 500.

13. A method in accordance with claim 1, wherein the nanofiber layer comprises a plurality of nanofibers, the nanofibers formed from polymers utilizing the electro-blown spinning process, the polymers comprising at least one of polyimides, polyamides, polyaramides, polybenzimidazoles, polyetherimides, polyacrylonitriles, polyethylene terephthalate, polypropylene, polyanilines, polyethylene oxides, polyethylene naphthalates, polybutylene terephthalate, styrene butadiene rubber, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyvinylidene chloride, polyvinyl butylenes, and copolymer or derivative compounds thereof.

14. A method in accordance with claim 1, further comprising pleating the composite filter media.