Filtration media for filtering particulate material from gas streams

• US 20060137317A1
• Filed: 12/07/2005
• Published: 06/29/2006
• Est. Priority Date: 12/28/2004
• Status: Abandoned Application

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Jones, David Charles, Bryner, Michael Allen, Lim, Hyun Sung, Hovanec, Joseph Brian, Wiseman, B. Lynne
• Application Number:
  US11/295,861
• Publication Number:
  US 20060137317A1
• Time in Patent Office: Days
• US Class Current: 55/528
• CPC Class Codes: B01D 2239/025 comprising nanofibres apparatus incorporating such gas filtering material see B01D46/546
• CPC Class Codes: B01D 2239/0681 The layers being joined by gluing
• CPC Class Codes: B01D 2239/10 Filtering material manufacturing
• CPC Class Codes: B01D 2273/28 Making use of vacuum or underpressure
• CPC Class Codes: B01D 2275/10 Multiple layers
• CPC Class Codes: B01D 39/1615 of natural origin
• CPC Class Codes: B01D 39/163 sintered or bonded
• CPC Class Codes: B01D 39/18 the material being cellulose or derivatives thereof cork or peat B01D39/1646 ; making filter paper D21F11/14
• CPC Class Codes: B01D 46/22 the belts travelling during filtering
• CPC Class Codes: B01D 46/521 using folded, pleated material
• CPC Class Codes: B01D 46/546 using nano- or microfibres
• CPC Class Codes: B32B 2250/20 All layers being fibrous or filamentary
• CPC Class Codes: B32B 2262/0261 Polyamide fibres
• CPC Class Codes: B32B 2307/544 Torsion strength; Torsion stiffness
• CPC Class Codes: B32B 2307/546 Flexural strength; Flexion stiffness
• CPC Class Codes: B32B 2459/00 Nets, e.g. camouflage nets
• CPC Class Codes: B32B 5/022 Non-woven fabric
• CPC Class Codes: B32B 5/024 Woven fabric
• CPC Class Codes: B32B 5/26 another layer next to it also being fibrous or filamentary relative arrangement of fibres or filaments of different layers B32B5/12
• 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 3/16 : with bonds between thermoplastic filaments produced in association with filament formation, e.g. immediately following extrusion

Abstract

A filtration medium is disclosed for use in air filters used in heating, ventilating and air conditioning systems. The medium contains at least one nanofiber layer of fibers having diameters less than 1 μm and at least one carrier layer, each nanofiber layer having a basis weight of at least about 2.5 g/m², and up to about 25 g/m². The medium has sufficient stiffness to be formed into a pleated configuration.

Claims

1. A filtration medium comprising at least one nanofiber layer of continuous polymeric fibers having diameters less than about 1000 nanometers, each nanofiber layer having a basis weight of at least about 2.5 g/m², and at least one scrim layer, wherein the medium has a filtration efficiency of at least about 20% when challenged with particles having an average diameter of 0.3 μ

m in air flowing at a face velocity of 5.33 cm/sec, and a Handle-o-meter stiffness of at least about 45 g.

2. The filtration medium of claim 1, wherein the total nanofiber layer basis weight is about 25 g/m².

3. The filtration medium of claim 1, wherein the nanofiber layer has a thickness of less than 100 μ

m.

4. The filtration medium of claim 1, wherein the wherein the continuous polymeric fibers of the nanofiber layer have diameters between about 100 nanometers and about 700 nanometers.

5. The filtration medium of claim 1, wherein the wherein the continuous polymeric fibers of the nanofiber layer have diameters between about 300 nanometers and about 650 nanometers.

6. The filtration medium of claim 1, wherein the medium has a filtration efficiency of at least about 30% and up to about 99.97% when challenged with particles having an average diameter of 0.3 μ

m in air flowing at a face velocity of 5.33 cm/sec.

7. The filtration medium of claim 1, further comprising a second scrim layer wherein the nanofiber layer is sandwiched between the two scrim layers.

8. The filtration medium of claim 1, wherein the medium is substantially electrically neutral.

9. The filtration medium of claim 1, wherein the scrim layer is a spunbond nonwoven web or carded nonwoven web.

10. The filtration medium of claim 1, which has an initial pressure drop less than about 30 mm H₂O.

11. The filtration medium of claim 1, which has an initial pressure drop less than about 24 mm H₂O.

12. The filtration medium of claim 1, which has a Frazier air permeability of at least about 0.91 m³/min/m².

13. The filtration medium of claim 1, which has a Frazier air permeability of between about 0.91 m³/min/m² and about 48 m³/min/m².

14. The filtration medium of claim 1, wherein the filtration medium is pleated.

15. A process for filtering particulate matter from an air stream comprising passing an air stream containing particulate matter through a filtration medium comprising at least one nanofiber layer of continuous polymeric fibers and at least one scrim layer, wherein the continuous polymeric fibers of the nanofiber layer have diameters less than about 1000 nanometers and wherein each nanofiber layer has a basis weight of at least about 2.5 g/m² and a thickness of less than about 100 μ

m, and wherein the filtration medium has a Handle-o-meter stiffness of at least about 45 g, and filtering up to about 99.97% of particles having an average diameter of 0.3 μ

m in an air stream moving at a face velocity of 5.33 cm/sec.

16. The process of claim 15, wherein at least 20% of particles 0.3 μ

m and larger are filtered.

17. The process of claim 15, wherein the initial pressure drop of the filtration medium is less than about 30 mm H₂O.

18. The process of claim 15, wherein the total basis weight of the nanofiber layer is about 25 g/m².

19. A process of forming a filtration medium comprising

providing at least one scrim layer having a Handle-o-meter stiffness of at least about 10 g on a moving collection belt, and

depositing nanofibers on the scrim layer to form a single nanofiber layer having a basis weight of at least about 2.5 g/m² to form a filtration medium having a Handle-o-meter stiffness of at least about 45 g and a pressure drop of less than about 30 mm H₂O.

20. The process of claim 19, wherein the total nanofiber layer basis weight is about 25 g/m².

21. The process of claim 20, wherein the nanofiber layer is formed in a single pass of the scrim layer on the moving collection belt.

22. The process of claim 19, wherein the nanofibers are formed by electroblowing a polymer solution from a series of spinneret holes at a rate of at least about 1 cm³/min/hole and the collection belt moves at a rate of at least 5 m/minute.

23. The process of claim 22, wherein the polymer solution is electroblown from a series of spinneret holes at a rate of at least 2 cm³/min/hole.

24. The process of claim 19, further comprising pleating the filtration medium.

25. The process of claim 19, further comprising adhering at least a second scrim layer onto said nanofiber layer.

26. The process of claim 19, wherein said scrim layer has a Handle-o-meter stiffness of at least about 45 g.

27. The process of claim 25, wherein said scrim layers have a combined Handle-o-meter stiffness of at least about 45 g.