Pleated aligned web filter

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.

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 μm.  
   
   
       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 μm.  
   
   
       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.