Filtration materials using fiber blends that contain strategically shaped fibers and/or charge control agents

Abstract

A filtration material comprising a blend of polypropylene and acrylic fibers of round, flat, dog bone, oval or kidney bean shape in any size from 0.08 to 3.3 Dtex. A preferred blend contains about 50 weight percent polypropylene fibers and about 50 weight percent acrylic fibers. The fibers can be blended ranging from 90:10 to 10:90 polypropylene to acrylic. The shape contains 25 weight percent round, flat, oval, dog bone and kidney bean shapes. The fiber blend contains 25 weight percent of at least one size between 0.08 and 3.3 Dtex. Electret fibers incorporated within these blends have 0.02 to 33 weight percent of a charge control agent. These fibers can be used in producing electret material by corona or triboelectric charging methods.

1 . An electret gas filter media made of non-woven fibers, the filter media comprising:
 (a) at least some of said non-woven fibers are acrylic fibers formed by a wet spinning process with a dog bone shaped cross section and containing no ferroelectric material; and   (b) about 0.5% to about 2% wax or other lubricant by weight on the outer surfaces of at least some of said non-woven fibers.   
     
     
         2 . The filter media in accordance with  claim 1 , wherein the filter media further comprises at least some polypropylene fibers. 
     
     
         3 . The filter media in accordance with  claim 2 , wherein at least some of the polypropylene fibers have dog bone shaped cross section. 
     
     
         4 . The filter media in accordance with  claim 1 , wherein a charge control agent or lubricant is disposed on the outer surfaces of at least some of the non-woven fibers. 
     
     
         5 . An electret gas filter media made of non-woven fibers, the filter media comprising:
 (a) at least some of said non-woven fibers are polypropylene fibers with a non-round cross section, at least some of which have a dog bone shaped cross section; and   (b) at least some of said non-woven fibers are acrylic fibers formed by a wet spinning process and having a dog bone shaped cross section.   
     
     
         6 . The filter media in accordance with  claim 5 , wherein a ratio of polypropylene fibers to acrylic fibers is in a range from about 90:10 to about 10:90. 
     
     
         7 . The filter media in accordance with  claim 5 , further comprising a charge control agent or lubricant disposed on the outer surfaces of at least some of the non-woven fibers. 
     
     
         8 . The filter media in accordance with  claim 7 , wherein said charge control agent or lubricant is selected from the group consisting of organic wax, non-organic wax and PVDF. 
     
     
         9 . An electret gas filter media made of non-woven fibers, the filter media comprising:
 (a) at least some of said non-woven fibers are polypropylene fibers and contain no ferroelectric material; and   (b) a charge control agent or lubricant is disposed on the outer surfaces of at least some of the non-woven fibers.   
     
     
         10 . The filter media in accordance with  claim 9 , wherein the filter media further comprises at least some acrylic fibers formed by a wet spinning process and having a dog bone shaped cross section. 
     
     
         11 . The filter media in accordance with  claim 10 , wherein the polypropylene fibers have a dog bone shaped cross section. 
     
     
         12 . The filter media in accordance with  claim 11 , wherein a ratio of polypropylene fibers to acrylic fibers is in a range from about 90:10 to about 10:90. 
     
     
         13 . The filter media in accordance with  claim 12 , wherein the polypropylene fibers have a round cross section. 
     
     
         14 . An electret gas filter media made of non-woven fibers, the filter media comprising:
 (a) at least some of said non-woven fibers are polypropylene fibers; and   (b) at least some of said non-woven fibers are acrylic fibers formed by a wet spinning process and having a non-round shaped cross section.   
     
     
         15 . The filter media in accordance with  claim 14 , wherein a ratio of polypropylene fibers to acrylic fibers is in a range from about 90:10 to about 10:90. 
     
     
         16 . The filter media in accordance with  claim 15 , wherein a ratio of polypropylene fibers to acrylic fibers is in a range from about 80:20 to about 20:80. 
     
     
         17 . The filter media in accordance with  claim 16 , wherein a ratio of polypropylene fibers to acrylic fibers is in a range from about 60:40 to about 40:60. 
     
     
         18 . The filter media in accordance with  claim 15 , further comprising a charge control agent or lubricant disposed on the outer surfaces of at least some of the non-woven fibers. 
     
     
         19 . The filter media in accordance with  claim 15 , wherein the polypropylene fibers have a non-round shaped cross section. 
     
     
         20 . The filter media in accordance with  claim 15 , wherein the polypropylene fibers have a round cross section.