Multi-phase filter medium

Abstract

Multi-phase filter media, as well as related articles, components, filter elements, and methods, are disclosed.

1 . (canceled) 
     
     
         2 . A filter medium, comprising:
 a first phase comprising a first plurality of fibers and a second plurality of fibers different from the first plurality of fibers;   a second phase comprising a third plurality of fibers and a fourth plurality of fibers different from the third plurality of fibers, the third plurality of fibers being the same as or different from the first or second plurality of fibers and the fourth plurality of fibers being the same as or different from the first or second plurality of fibers; and   a transition phase between the first and second phases, wherein the transition phase comprises at least a portion of the first plurality of fibers, at least a portion of the second plurality of fibers, at least a portion of the third plurality of fibers, and at least a portion of the fourth plurality of fibers, and wherein at least a portion of the first plurality of fibers, at least a portion of the second plurality of fibers, at least a portion of the third plurality of fibers, and at least a portion of the fourth plurality of fibers are intermingled with each other,   wherein the air permeability of the first plurality of fibers is higher than the air permeability of the second plurality of fibers, the air permeability of the third plurality of fibers is higher than the air permeability of the fourth plurality of fibers,   wherein a weight ratio of the first plurality of fibers to the second plurality of fibers is from about 50:50 to about 97:3,   wherein the basis weight ratio of the first phase to the second phase is from about 30:70 to about 70:30,   wherein the first and second phases form a wet laid structure,   wherein the first, second, third and fourth pluralities of fibers are wet laid,   wherein the filter medium has a dust holding capacity from about 1 g to about 3 g measured according to a Palas flat sheet test.   
     
     
         3 . The filter medium of  claim 2 , wherein the air permeability of the second or fourth plurality of fibers is from about 5 CFM to about 50 CFM. 
     
     
         4 . The filter medium of  claim 2 , wherein the air permeability of the second plurality of fibers is from about 15 CFM to about 25 CFM. 
     
     
         5 . The filter medium of  claim 2 , wherein the air permeability of the first or third plurality of fibers is from about 50 CFM to about 350 CFM. 
     
     
         6 . The filter medium of  claim 2 , wherein the air permeability of the first or third plurality of fibers is from about 100 CFM to about 200 CFM. 
     
     
         7 . The filter medium of  claim 2 , wherein the filter medium comprises a binder. 
     
     
         8 . The filter medium of  claim 7 , wherein the binder is at most 35% of the basis weight of the filter medium. 
     
     
         9 . The filter medium of  claim 7 , wherein the binder is at most 25% of the basis weight of the filter medium. 
     
     
         10 . The filter medium of  claim 8 , wherein the binder comprises polyvinyl acetate, an epoxy, a polyester, a polyvinyl alcohol, and/or an acrylic. 
     
     
         11 . The filter medium of  claim 2 , wherein each of the first, second, third, and fourth fibers are formed of an organic polymeric material. 
     
     
         12 . The filter medium of  claim 2 , wherein the filter medium has an air permeability of about 2 CFM to about 200 CFM. 
     
     
         13 . The filter medium of  claim 2 , wherein the weight ratio of first to second phase is from about 40:60 to about 60:40. 
     
     
         14 . The filter medium of  claim 2 , wherein the first phase comprises mixture of softwood fibers and hardwood fibers. 
     
     
         15 . The filter medium of  claim 2 , wherein the first or third plurality of fibers have an average fiber length from about 1.5 mm to about 6 mm. 
     
     
         16 . The filter medium of  claim 2 , wherein the second or fourth plurality of fibers have an average fiber length of from about 0.5 mm to about 2 mm. 
     
     
         17 . The filter medium of  claim 2 , wherein the first phase has a higher air permeability than the second phase, wherein a weight ratio of the first and second pluralities of fibers is from about 60:40 to about 90:10, and a weight ratio of the third and fourth pluralities of fibers is from about 10:90 to about 50:50, and wherein the air permeability of the first or third plurality of fibers is from 100 CFM to 200 CFM. 
     
     
         18 . The filter medium of  claim 2 , wherein at least two of the first, second, third and fourth pluralities of fibers are either hardwood or softwood fibers. 
     
     
         19 . The filter medium of  claim 2 , wherein the filter medium includes a weight ratio of the first and second pluralities of fibers of from about 50:50 to about 90:10, and a weight ratio of the third and fourth pluralities of fibers of from about 10:90 to about 50:50. 
     
     
         20 . The filter medium of  claim 2 , wherein the mean flow pore size of filter medium is at least about 25 microns. 
     
     
         21 . The filter medium of  claim 2 , wherein the filter medium has a mean flow pore size of from about 25 microns to about 125 microns. 
     
     
         22 . The filter medium of  claim 2 , wherein the filter medium has an initial dust capture efficiency from about 80% to about 99.5%. 
     
     
         23 . The filter medium of  claim 2 , wherein the first phase has a higher air permeability than the second phase, wherein a weight ratio of the first and second pluralities of fibers is from about 60:40 to about 90:10, and a weight ratio of the third and fourth pluralities of fibers is from about 10:90 to about 50:50, wherein the filter medium comprises a binder, and wherein the binder is at most 25% of the basis weight of the filter medium. 
     
     
         24 . The filter medium of  claim 2 , wherein the first phase has a higher air permeability than the second phase, wherein a weight ratio of the first and second pluralities of fibers is from about 60:40 to about 90:10, and a weight ratio of the third and fourth pluralities of fibers is from about 10:90 to about 50:50, and wherein the mean flow pore size of filter medium is at least about 25 microns.