Pleated aligned web filter

• US 20050217226A1
• Filed: 04/05/2004
• Published: 10/06/2005
• Est. Priority Date: 04/05/2004
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Sundet, Douglas C., Shah, Rahul, Brandner, John M., Wu, Tien T.
• Application Number:
  US10/818,091
• Publication Number:
  US 20050217226A1
• Time in Patent Office: Days
• US Class Current: 55/521
• 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 that has rows of folded pleats and includes a nonwoven filtration web that contains thermoplastic fibers, a majority of which fibers are aligned at 90°±20° with respect to the row direction. The filter elements 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.

Claims

1. A filter element that comprises:

a nonwoven filtration web that has rows of folded pleats and that contains thermoplastic fibers, a majority of which fibers 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 pleats in a nonwoven filtration web that comprises thermoplastic fibers, a majority of which fibers are aligned at 90°

±

20°

with respect to the row direction;

and cutting the pleated filter element to a desired size and shape.

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.