Meltblown filter medium

Abstract

Filter media, as well as related assemblies, systems and methods. Filter media may contain one or more layers formed of a meltblown material.

1 . A method of forming a meltblown fiber web comprising:
 extruding a polymer melt through a die to form a polymer extrudate;   impinging the extrudate with process air when forming polymer fibers from the extrudate, wherein the process air volume is greater than 2500 pounds/hour-meter; and   collecting the polymer fibers on a collector to form a meltblown fiber web, while applying a vacuum of at least 10 inches of water, wherein an average diameter of the polymer fibers is at most 1.5 microns.   
     
     
         2 . The method of  claim 1 , wherein the average diameter of the polymer fibers is at most 1.0 microns. 
     
     
         3 . The method of  claim 1 , wherein the average diameter of the polymer fibers is at least 0.2 micron. 
     
     
         4 . The method of  claim 1 , wherein the process air volume is at least 2750 pounds/hour-meter and at most 4000 pounds/hour-meter. 
     
     
         5 . The method of  claim 1 , wherein the vacuum is at least 14 inches of water. 
     
     
         6 . The method of  claim 1 , wherein the vacuum is at least 14 inches of water and at most 26 inches of water. 
     
     
         7 . The method of  claim 1 , wherein the collector speed is at least 10 feet/min. 
     
     
         8 . The method of  claim 1 , wherein the polymer melt is extruded through a die tip having a series of holes to form the polymer extrudate. 
     
     
         9 . The method of  claim 1 , wherein the polymer melt is heated to a temperature of at least 350° F. in the extruder. 
     
     
         10 . The method of  claim 1 , wherein the meltblown fiber web has a basis weight of at least 1 g/m 2  and at most 100 g/m2. 
     
     
         11 . The method of  claim 1 , wherein the meltblown fiber web has a thickness of at least five microns to at most 250 microns. 
     
     
         12 . The method of  claim 1 , wherein the air permeability of the meltblown fiber web is at least 20 CFM to at most 500 CFM. 
     
     
         13 . The method of  claim 1 , further comprising forming a filter medium comprising the meltblown fiber web. 
     
     
         14 . The method of  claim 13 , wherein the filter medium includes a substrate that supports the meltblown fiber web. 
     
     
         15 . The method of  claim 1 , wherein the process air comprises heated air on sides of the die tip where the fibers are formed. 
     
     
         16 . The method of  claim 1 , wherein the process air helps attenuate the polymer fibers to a final fiber size.