PLEATED FILTER WITH MONOLAYER MONOCOMPONENT MELTSPUN MEDIA

• US 20080022642A1
• Filed: 07/31/2006
• Published: 01/31/2008
• Est. Priority Date: 07/31/2006
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Stelter, John D., Fox, Andrew R., Angadjivand, Seyed A., Sundet, Douglas C., Fay, William T., Berrigan, Michael R.
• Granted Patent: US 7,947,142 B2
• Time in Patent Office: Days
• US Class Current: 55/521
• CPC Class Codes: B01D 39/163 sintered or bonded
• CPC Class Codes: B01D 46/521 using folded, pleated material
• CPC Class Codes: D04H 3/005 Synthetic yarns or filaments D04H3/013 takes precedence
• CPC Class Codes: D04H 3/14 with bonds between thermoplastic yarns or filaments produced by welding
• CPC Class Codes: D04H 3/16 with bonds between thermoplastic filaments produced in association with filament formation, e.g. immediately following extrusion
• CPC Class Codes: Y10T 156/1015 Folding

Abstract

A pleated filter is made from a monocomponent monolayer nonwoven web of continuous monocomponent meltspun partially crystalline and partially amorphous oriented fibers of the same polymeric composition that are bonded to form a coherent and handleable web having a Gurley Stiffness of at least 100 mg and which further may be softened while retaining orientation and fiber structure. Rows of pleats are formed in the nonwoven web, and the web is cut to a desired size and shape to provide a pleated filter element containing a self-supporting porous monocomponent monolayer matrix of fibers bonded to one another at at least some points of fiber intersection and having an average initial submicron efficiency of at least 15% at a 1.52 meters/sec face velocity. The filter element is deformation resistant without requiring stiffening layers, bicomponent fibers, adhesive or other reinforcement in the filter media layer.

Claims

1. A process for making a pleated filter comprising:

a) forming a monocomponent monolayer nonwoven web of continuous monocomponent polymeric fibers by meltspinning, collecting, heating and quenching the monocomponent polymeric fibers under thermal conditions sufficient to form a web of partially crystalline and partially amorphous oriented meltspun fibers of the same polymeric composition that are bonded to form a coherent and handleable web having a Gurley Stiffness of at least 100 mg and which further may be softened while retaining orientation and fiber structure,

b) forming rows of pleats in the nonwoven web, and

c) cutting the pleated web to a desired size and shape to form a pleated filter element comprising a self-supporting porous monocomponent monolayer matrix of fibers bonded to one another at at least some points of fiber intersection and having an average initial submicron efficiency of at least 15% at a 1.52 meters/sec face velocity.

2. A process according to claim 1 wherein the fibers are autogenously bonded.

3. A process according to claim 1 comprising forming the pleats by heating the web to a temperature at least 10°

C. less than the Nominal Melting Point of the fibers.

4. A process according to claim 1 wherein the web has a basis weight of about 65 to about 250 grams/m².

5. A process according to claim 1 wherein the web has an Effective Fiber Diameter of about 8 to about 40 μ

m.

6. A process according to claim 1 wherein the web has a Gurley Stiffness of at least about 200 mg.

7. A process according to claim 1 wherein the web has a Gurley Stiffness of at least about 300 mg.

8. A process according to claim 1 wherein the polymer is polypropylene.

9. A process according to claim 1 wherein the web has an initial filtration quality factor QF of at least about 0.3 when exposed to a DOP challenge aerosol containing particles with a diameter of about 0.185 μ

m at an airborne concentration of about 100 mg/m³, flowing at a 13.8 cm/sec face velocity.

10. A process according to claim 1 wherein the web has an initial filtration quality factor QF of at least about 0.4 when exposed to a DOP challenge aerosol containing particles with a diameter of about 0.185 μ

m at an airborne concentration of about 100 mg/m³, flowing at a 13.8 cm/sec face velocity.

11. A process according to claim 1 wherein the pleated filter element has an average initial sub-micron efficiency of at least about 25%.

12. A process according to claim 1 wherein the pleated filter element has an average initial sub-micron efficiency of at least about 50%.

13. A process according to claim 1 further comprising charging the web.

15. A process according to claim 1 further comprising calendaring the web.

14. A process according to claim 14 comprising hydrocharging the web.

16. A pleated filter comprising a self-supporting porous monocomponent monolayer matrix of partially crystalline and partially amorphous oriented meltspun polymeric fibers of the same polymeric composition bonded to one another at at least some points of fiber intersection, the matrix being formed into rows of folded or corrugated pleats and having an average initial submicron efficiency of at least 15% at a 1.52 meters/sec face velocity.

17. A pleated filter according to claim 16 wherein the fibers are autogenously bonded.

18. A pleated filter according to claim 16 wherein the polymer is polypropylene.

19. A pleated filter according to claim 16 wherein the matrix has a basis weight of about 65 to about 250 grams/m².