Coalescing filter media

Abstract

Filter media, filter elements, and methods for filtering an gas stream are described herein. In some embodiments, the filter media may comprise a fiber web comprising a plurality of fibers and having a particular oil repellency level. For instance, in certain embodiments, the surface chemistry of the fiber web may be tailored to impart a particular surface energy density that matches the surface energy density of the fluid (e.g., an oil, a lubricant, and/or a cooling agent) being removed from the gas stream. In some embodiments, the fiber web may be wrapped around a core. For example, the fiber web may be wrapped around the core such that it forms two or more layers around the core. In some cases, the fiber web may be perforated. In certain embodiments, an gas stream comprising a fluid (e.g., an oil, a lubricant, and/or a cooling agent) may be passed through the fiber web, filter media, and/or filter element such that at least a portion of the fluid coalesces on the fiber web. Fiber webs, filter media, and/or filter elements as described herein may be particularly well-suited for applications that involve filtering gas streams containing oil, lubricants, and/or cooling agents (e.g., gas streams generated by a compressor) though the media may also be used in other applications. Advantageously, the fiber webs, filter media, and/or filter elements described herein may significantly reduce or prevent fouling of the filter caused by oil or other liquids.

What is claimed is: 
     
         1 . (canceled) 
     
     
         2 . A filter element, comprising:
 a core; and   a fiber web wrapped around the core, wherein the fiber web comprises:   a plurality of fibers having an average fiber diameter of at least 0.01 microns and less than or equal to 50 microns;   wherein at least one surface of the fiber web comprises a coating, the coating comprising a fluorinated polymer,   wherein the fiber web has an oil repellency level of between 4 or greater and 6 or less, and wherein the fiber web has an oil carry over of less than 20%.   
     
     
         3 . A filter element as in  claim 2 , wherein the fiber web is pleated. 
     
     
         4 . A filter element as in  claim 2 , wherein the filter element comprises at least two layers of the fiber web. 
     
     
         5 . A filter element as in  claim 2 , wherein the core comprises a wire mesh. 
     
     
         6 . A filter media, comprising:
 a fiber web, wherein the fiber web comprises:   a plurality of fibers having an average fiber diameter of at least 0.01 microns and less than or equal to 50 microns;   wherein at least one surface of the fiber web comprises a coating, the coating comprising a fluorinated polymer,   wherein the fiber web has an oil repellency level of between 4 or greater and 6 or less, and   wherein the fiber web comprises a plurality of perforations having an average cross-sectional dimension of at least about 1 mm.   
     
     
         7 . A filter element as in  claim 2 , wherein the filter element comprises a support layer. 
     
     
         8 . A filter element as in  claim 7 , wherein the support layer comprises a plurality of fibers. 
     
     
         9 . A filter element as in  claim 2 , wherein a weight percentage of binder fibers present in the fiber web is at least about 0 wt % and less than or equal to about 10 wt %. 
     
     
         10 . A filter element as in  claim 2 , wherein the fiber web is corrugated and/or embossed. 
     
     
         11 . A filter element as in  claim 2 , wherein the coating comprises a plurality of small molecules. 
     
     
         12 . A filter element as in  claim 11 , wherein the small molecules comprises a fluorocarbon having the formula —C n F 2n+1  or —C n F m , wherein n is an integer greater than 1, and wherein m is an integer greater than 1. 
     
     
         13 . A filter element as in  claim 2 , wherein the coating is a fluorocarbon selected from the group consisting of CF 4 , C 2 F 4 , C 3 F 6 , C 3 F 8 , C 4 H 8 , C 5 H 12 , C 6 F 6 , C 6 F 13 . 
     
     
         14 . A filter element as in  claim 2 , comprising glass fibers, wherein the weight percentage of glass fibers present in the fiber web is greater than or equal to about 0% and less than or equal to about 99% by weight of the total fibers in the fiber web. 
     
     
         15 . A filter element as in  claim 2 , comprising synthetic fibers, wherein the weight percentage of synthetic fibers present in the web is greater than or equal to about 1% and less than or equal to about 100% by weight of the total fibers in the fiber web. 
     
     
         16 . A filter element as in  claim 2 , comprising cellulose fibers, wherein the weight percentage of cellulose fibers present in the fiber web is greater than or equal to about 1% and less than or equal to about 100% by weight of the total fibers in the fiber web. 
     
     
         17 . A filter element as in  claim 2 , wherein the fiber web has at least one modified surface. 
     
     
         18 . A filter element as in  claim 11 , wherein the small molecules are deposited on the at least one surface via chemical vapor deposition. 
     
     
         19 . A filter element as in  claim 2 , wherein the fiber web has an initial efficiency of greater than or equal to about 80% and less than or equal to about 99.99%. 
     
     
         20 . A system comprising the filter element as in  claim 2 , wherein the filter element is positioned downstream of a device for generating a gas stream including an oil, lubricant, and/or cooling agent, wherein the oil, lubricant, and/or cooling agent has a surface tension of between 22 mN/m and 33 mN/m measured at 23° C. and 50% RH. 
     
     
         21 . A system as in  claim 20 , wherein the device comprises a compressor, a distillation column, an evaporator, a thermal oil ventilator, a crankcase ventilator, a combustion engine, and/or an exhaust conduit.