Pleated Aligned Web Filter

• US 20060246260A1
• Filed: 07/17/2006
• Published: 11/02/2006
• Est. Priority Date: 04/05/2004
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Sundet, Douglas C., Shah, Rahul R.
• Granted Patent: US 7,622,063 B2
• Time in Patent Office: Days
• US Class Current: 428/174
• CPC Class Codes: B01D 39/1623 of synthetic origin
• CPC Class Codes: Y10S 55/05 Methods of making filter
• CPC Class Codes: Y10T 428/24628 Nonplanar uniform thickness material
• CPC Class Codes: Y10T 428/24686 Pleats or otherwise parallel adjacent folds
• CPC Class Codes: Y10T 442/60 Nonwoven fabric [i.e., nonwoven strand or fiber material]
• CPC Class Codes: Y10T 442/643 Including parallel strand or fiber material within the nonwoven fabric

Abstract

A filter element in the form of a nonwoven self-supporting filtration web having rows of folded or corrugated spaced-apart pleats, the web containing continuous thermoplastic fibers a majority of which are aligned at 90°±20° with respect to the row direction. The filter element can be made by forming rows of pleats in such a nonwoven web and cutting the web to a desired size and shape. The filter elements can provide improved mechanical and filtration properties and can exhibit reduced susceptibility to pleat deformation and the loss of space between pleats.

Claims

1. A filter element that comprises a nonwoven self-supporting filtration web having rows of folded or corrugated spaced-apart pleats and that contains continuous thermoplastic fibers a majority of which are aligned at 90°

±

20°

with respect to the row direction.

2. A filter element according to claim 1 wherein about 55 to about 90% of the fibers are aligned at 90°

±

20°

with respect to the row direction.

3. A filter element according to claim 1 wherein about 70 to about 85% of the collected fibers are aligned at 90°

±

20°

with respect to the row direction.

4. A filter element according to claim 1 wherein fibers having lengths of about 2-5 cm can be teased from the web.

5. A filter element according to claim 1 wherein the fibers have an average effective fiber diameter of about 8 to about 25 μ

m.

6. A filter element according to claim 1 wherein the web has at least a 2:

1 ratio of the in-plane tensile strength in the direction transverse to the row direction to the tensile strength in the row direction using a 50 mm gauge length.

7. A filter element according to claim 1 wherein the web has at least a 4:

1 ratio of the in-plane tensile strength in the direction transverse to the row direction to the tensile strength in the row direction using a 50 mm gauge length.

8. A filter element according to claim 1 wherein the web has at least a 2:

1 ratio of the in-plane Taber Stiffness in the direction transverse to the row direction to the Taber Stiffness in the row direction.

9. A filter element according to claim 1 wherein the web has at least a 2.2:

1 ratio of the in-plane Taber Stiffness in the direction transverse to the row direction to the Taber Stiffness in the row direction.

10. A filter element according to claim 1 wherein the major surfaces of the web exhibit striations corresponding to substantial alignment of individual fibers transverse to the row direction.

11. A filter element according to claim 1 wherein a wetting fluid placed on the web preferentially wicks transverse to the row direction.

12. A filter element according to claim 1 wherein the web has been annealed.

13. A filter element according to claim 1 wherein the web has been corona-treated or hydrocharged.

14. A method of making a pleated filter element, which method comprises:

forming rows of spaced-apart pleats in a nonwoven filtration web that comprises continuous thermoplastic fibers a majority of which are aligned at 90°

±

20°

with respect to the row direction; and

cutting the pleated web to a desired size and shape to form a self-supporting pleated filter element.

15. A method according to claim 14 wherein about 55 to about 90% of the fibers are aligned at 90°

±

20°

with respect to the row direction.

16. A method according to claim 14 wherein about 70 to about 85% of the collected fibers are aligned at 90°

±

20°

with respect to the row direction.

17. A method according to claim 14 wherein fibers having lengths of about 2-5 cm can be teased from the web.

18. A method according to claim 14 wherein the fibers have an average effective fiber diameter of about 8 to about 25 μ

m.

19. A method according to claim 14 wherein the web has at least a 2:

1 ratio of the in-plane tensile strength in the direction transverse to the row direction to the tensile strength in the row direction using a 50 mm gauge length.

20. A method according to claim 19 wherein the web has a filtration quality factor Q_F of at least about 0.6 using 100 ppm dioctyl phthalate particles having a size range between 10 and 700 nm traveling at a 7 cm/sec face velocity.

21. A method according to claim 14 wherein the web has at least a 4:

1 ratio of the in-plane tensile strength in the direction transverse to the row direction to the tensile strength in the row direction using a 50 mm gauge length.

22. A method according to claim 14 wherein the web has at least a 2:

1 ratio of the in-plane Taber Stiffness in the direction transverse to the row direction to the Taber Stiffness in the row direction.

23. A method according to claim 14 wherein the web has at least a 2.2:

1 ratio of the in-plane Taber Stiffness in the direction transverse to the row direction to the Taber Stiffness in the row direction.

24. A method according to claim 14 wherein the major surfaces of the web exhibit striations corresponding to substantial alignment of individual fibers transverse to the row direction.

25. A method according to claim 14 wherein a wetting fluid placed on the web preferentially wicks transverse to the row direction.

26. A method according to claim 14 wherein the web has been annealed.

27. A method according to claim 14 wherein the web has been corona-treated or hydrocharged.

28. A method according to claim 20 wherein the web has a filtration quality factor Q_F of at least about 0.6 using 100 ppm dioctyl phthalate particles having a size range between 10 and 700 nm traveling at a 7 cm/sec face velocity.