Filter having melt-blown and electrospun fibers

1. A multi-layer filter media, comprising:

at least one melt-blown fiber filter media layer having a basis weight of greater than 40 grams/m 2 and a median fiber diameter of at least 1 micron and less than 50 micron; and

at least one electrospun nanofiber media layer downstream of the at least one melt-blown fiber filter media layer, the at least one electrospun nanofiber media layer comprising fibers having a median fiber diameter of less than 0.8 micron and having a basis weight of greater than 0.010 grams/m 2 .

2. The multi-layer filter media of claim 1 , wherein the at least one melt-blown fiber filter media layer has a layer thickness of at least 1 mm.

3. The multi-layer filter media of claim 1 , wherein the basis weight of the at least one melt-blown fiber filter media layer is greater than 70 grams/m 2 .

4. The multi-layer filter media of claim 1 , wherein the basis weight of the at least one melt-blown fiber filter media layer is greater than 90 grams/m 2 .

5. The multi-layer filter media of claim 1 , wherein the at least one melt-blown fiber filter media has Frazier air permeability at a differential pressure of 0.5 inch of water between 400 CFM and 600 CFM.

6. The multi-layer filter media of claim 1 , wherein the multi-layer filter media has an initial pressure drop of less than 22 Pa.

7. The multi-layer filter media of claim 1 , further comprising a first scrim layer, wherein the at least one melt-blown fiber media layer includes a first melt-blown fiber media layer and the at least one electrospun nanofiber media layer includes a first electrospun nanofiber media layer, wherein the first electrospun nanofiber media layer is electrospun and on a downstream surface of the first melt-blown fiber filter media layer, wherein the first scrim layer is bonded to and downstream of the first electrospun nanofiber media, wherein the multi-layer filter media comprises at least three layers including the first melt-blown fiber filter media upstream of the first electrospun nanofiber filter media and the first scrim layer downstream of the first electrospun nanofiber media layer.

8. The multi-layer filter media of claim 1 , further comprising a first scrim layer, wherein the at least one melt-blown fiber media layer includes a first melt-blown fiber media layer and the at least one electrospun nanofiber media layer includes a first electrospun nanofiber media layer, wherein the first electrospun nanofiber media layer is electrospun and on a downstream surface of the first scrim layer, wherein the multi-layer filter media comprises at least three layers including the first melt-blown fiber filter media upstream of the first scrim layer, and the first electrospun nanofiber filter media downstream of the first scrim layer.

9. The multi-layer filter media of claim 8 , wherein the first scrim layer has thickness of at least 0.1 mm and less than 0.5 mm, average fiber size between 1 micron and 50 micron, and Frazier air porosity at 0.5 inch of water between 500 CFM and 600 CFM.

10. The multi-layer filter media of claim 8 , wherein the multi-layer filter media has a thickness between 1.5 mm and 2 mm, a filtration efficiency greater than 90% for 1 micron particle size, and an initial pressure drop of less than 22 Pa.

11. The multi-layer filter media of claim 1 , further comprising a first scrim layer and a second scrim layer, wherein the at least one melt-blown fiber filter media layer includes a first melt-blown fiber media layer and the at least one electrospun nanofiber media layer includes a first electrospun nanofiber media layer, wherein the multi-layer filter media comprises at least four layers including the first scrim layer bonded to a downstream surface of the first melt-blown fiber media layer, the first electrospun nanofiber layer electrospun on a downstream surface of the first scrim layer, and the second scrim layer bonded to a downstream surface of the first electrospun nanofiber layer.

12. The multi-layer filter media of claim 11 , further comprising a second melt-blown fiber filter media layer bonded to upstream of the first melt-blown fiber filter media layer.

13. The multi-layer filter media of claim 1 , further comprising a first scrim layer, wherein the at least one melt-blown fiber filter media layer includes a first melt blown fiber filter media layer and a second melt-blown fiber filter media layer, and the at least one electrospun nanofiber media layer includes a first electrospun nanofiber media layer, wherein the multi-layer filter media comprises at least four layers including the second melt-blown fiber filter layer bonded to a downstream surface of the first melt-blown fiber filter media layer, and the first electrospun nanofiber media layer electrospun and on a downstream surface of the second melt-blown fiber filter media layer, and the first scrim layer bonded to a downstream surface of the first electrospun nanofiber layer.

14. The multi-layer filter media of claim 1 , further comprising a first scrim layer, wherein the at least one melt-blown fiber filter media layer includes a first melt blown fiber filter media layer and a second melt-blown fiber filter media layer, and the at least one electrospun nanofiber media layer includes a first electrospun nanofiber media layer, wherein the multi-layer filter media comprises at least four layers including the second melt-blown fiber filter layer bonded to a downstream surface of the first melt-blown fiber filter media layer, and the first electrospun nanofiber media layer electrospun on an upstream surface of the scrim layer, and an upstream surface of the first electrospun nanofiber media layer bonded to a downstream surface of the second melt-blown fiber filter media layer.

15. The multi-layer filter media of claim 1 , wherein the multi-layer filter media is formed in a consolidated structural configuration.

16. The multi-layer media of claim 15 , wherein the multi-layer filter media is pleated.

17. The multi-layer filter media of claim 1 wherein the at least one melt-blown fiber filter media layer is depth loaded.

18. The multi-layer filter media of claim 17 wherein the at least one electrospun nanofiber media layer is depth loaded.

19. A method of forming a multi-layer filter media, comprising steps of:

providing a melt-blown fiber filter media layer by melt blowing a web of a polymer fibers having a median fiber diameter of at least 1 micron and less than 50 micron to form the melt-blown fiber filter media layer having a basis weight of greater than 40 grams/m 2 ;

providing a nanofiber media layer by electrospinning nanofibers having a median fiber diameter of less than 0.8 micron to form the nanofiber layer having a basis weight of greater than 0.010 grams/m 2 ; and

bonding the nanofiber layer to downstream of the melt-blown fiber filter media layer.

20. The method of claim 19 , wherein bonding the nanofiber media layer comprises electrospinning nanofibers onto a downstream surface of the melt-blown fiber filter media layer.

21. The method of claim 19 , wherein bonding the nanofiber media layer comprises electrospinning nanofibers onto a downstream surface of a scrim layer, and laminating the melt-blown fiber onto a upstream surface of the scrim layer.

22. The method of claim 19 , further including enhancing bonding between layers of the multi-layer filter media by pressure bonding, wherein the multi-layer filter media is compressed through a set of calendaring rollers.

23. The method of claim 19 , further including enhancing bonding between layers of the multi-layer filter media by heat bonding, wherein the multi-layer filter media is heated to a glass transition temperature of a polymer comprising the nanofiber media layer.