Pre-coalescing multi-layered filter media

Abstract

Fiber webs that may be used as filter media are provided. In some embodiments, the filter media may include multiple layers. Each layer may be designed to have separate functions in the filter media. For example, a first layer may be provided for improving dust holding capacity, a second layer for improving efficiency, and a third layer for providing support and strength to the media. By designing the layers to have separate functions, each layer may be optimized to enhance its function without negatively impacting the performance of another layer of the media.

What is claimed is: 
     
         1 . A filter media, comprising:
 a first layer comprising a first plurality of fibers;   a second layer comprising a second plurality of fibers; and   a third layer comprising cellulose fibers, wherein the third layer has an air permeability of greater than or equal to about 15 L/m 2 /sec and less than or equal to 2000 L/m 2 /sec, and a Mullen Burst strength of greater than or equal to about 100 kPa and less than or equal to 1,000 kPa;   wherein the second layer is positioned between the first and third layers; and   wherein a surface of at least one layer is modified to be hydrophobic or hydrophilic.   
     
     
         2 . The filter media of  claim 1 , wherein the second plurality of fibers comprises glass fibers, fibrillated fibers, and/or binder fibers. 
     
     
         3 . The filter media of  claim 1 , wherein the first plurality of fibers comprises synthetic fibers. 
     
     
         4 . The filter media of  claim 3 , wherein the synthetic fibers comprise continuous fibers. 
     
     
         5 . The filter media of  claim 4 , wherein the continuous fibers comprise meltblown fibers and/or spunbond fibers. 
     
     
         6 . The filter media of  claim 1 , wherein the third layer has a basis weight of greater than or equal to 50 gsm and less than or equal to 200 gsm. 
     
     
         7 . The filter media of  claim 1 , wherein the second layer has a basis weight of greater than or equal to 0.5 gsm and less than or equal to 100 gsm. 
     
     
         8 . The filter media of  claim 1 , wherein the first layer has an average fiber diameter of greater than or equal to 0.5 microns and less than or equal to 50 microns. 
     
     
         9 . The filter media of  claim 1 , wherein the second layer comprises sub-layers. 
     
     
         10 . The filter media of  claim 1 , wherein the third layer has a thickness of greater than or equal to 0.1 mm and less than or equal to 2 mm. 
     
     
         11 . The filter media of  claim 1 , wherein the cellulose fibers have an average fiber diameter of greater than or equal to 1 micron and less than or equal to 50 microns. 
     
     
         12 . The filter media of  claim 1 , wherein the filter media has a basis weight of greater than or equal to 50 gsm and less than or equal to 500 gsm. 
     
     
         13 . The filter media of  claim 1 , wherein the filter media has a dust holding capacity of greater than or equal to 50 gsm and less than or equal to 500 gsm. 
     
     
         14 . The filter media of  claim 1 , further comprising a fourth layer. 
     
     
         15 . The filter media of  claim 14 , wherein the fourth layer is a spunbond layer. 
     
     
         16 . The filter media of  claim 1 , wherein one or more layers comprises bicomponent fibers. 
     
     
         17 . The filter media of  claim 1 , wherein the second layer and/or third layer is modified to be hydrophobic. 
     
     
         18 . The filter media of  claim 1 , wherein the second layer and/or third layer is modified to be hydrophilic. 
     
     
         19 . The filter media of  claim 1 , wherein the first layer and/or the third layer is substantially free of glass fibers. 
     
     
         20 . The filter media of  claim 1 , wherein filter media is substantially free of glass fibers.