Fine fiber filter media and processes

Abstract

Fine fiber products including fiber webs, as well as related assemblies, systems and methods, are described. In some embodiments, fiber webs described herein may include fine fibers and relatively low amounts of degraded polymer formed during a fiber extrusion process. The fiber webs may be used for filter media applications.

1 . A fiber web comprising:
 a plurality of meltblown fibers having an average fiber diameter between about 0.1 microns and about 1.5 microns, wherein the fiber web has:   an air permeability between about 10 and about 1800 CFM;   a surface area greater than about 2.0 m 2 /g;   a basis weight between about 1.0 g/m 2  and about 100 g/m 2 ; and   a thickness between about 0.0005 inches and about 0.04 inches.   
     
     
         2 . The fiber web of  claim 1 , wherein the fiber web has a surface area greater than about 3.0 m 2 /g. 
     
     
         3 . The fiber web of  claim 1 , wherein the fiber web has a basis weight between about 3.0 g/m 2  and about 30 g/m 2 . 
     
     
         4 . The fiber web of  claim 1 , wherein the fiber web has a consistency of basis weight across the fiber web of about 3.0 standard deviations or less. 
     
     
         5 . The fiber web of  claim 1 , wherein the fiber web has a thickness between about 0.002 inches and about 0.010 inches. 
     
     
         6 . The fiber web of  claim 1 , wherein the fiber web has a consistency of thickness across the fiber web of about 3.0 standard deviations or less. 
     
     
         7 . The fiber web of  claim 1 , wherein the plurality of meltblown fibers have an average fiber diameter of less than about 1.0 microns. 
     
     
         8 . The fiber web of  claim 1 , wherein the plurality of meltblown fibers have an average fiber diameter of less than about 0.6 microns. 
     
     
         9 . A filter element comprising the fiber web of  claim 1 . 
     
     
         10 . A method of forming a fiber web comprising:
 introducing a polymeric material into an extrusion system including an extruder inlet, a die outlet, and a processing space between the extruder inlet and the die outlet, wherein the extrusion system comprises a extruder barrel having an inner diameter of about 4 inches or less;   processing the polymeric material in the extrusion system such that the polymeric material has a dwell time of less than about 85 minutes in the processing space;   forming a plurality of meltblown fibers from the polymeric material, wherein the plurality of meltblown fibers have an average diameter between about 0.1 microns and about 1.5 microns; and   forming a fiber web comprising the plurality of meltblown fibers.   
     
     
         11 . The method of  claim 10 , wherein the extrusion system comprises a extruder barrel having an inner diameter of about 3 inches or less. 
     
     
         12 . The method of  claim 10 , wherein the extrusion system comprises a extruder barrel having an inner diameter of about 2 inches or less. 
     
     
         13 . The method of  claim 10 , comprising processing the polymeric material in the extrusion system such that the polymeric material has a dwell time of less than about 60 minutes in the processing space. 
     
     
         14 . The method of  claim 10 , comprising processing the polymeric material in the extrusion system such that the polymeric material has a dwell time of less than about 40 minutes in the processing space. 
     
     
         15 . The method of  claim 10 , wherein the plurality of meltblown fibers have an average diameter between about 0.1 microns and about 1.0 microns. 
     
     
         16 . The method of  claim 10 , wherein the plurality of meltblown fibers have an average diameter between about 0.1 microns and about 0.6 microns. 
     
     
         17 . A filter element comprising the fiber web of  claim 10 . 
     
     
         18 . A method of forming a fiber web comprising:
 introducing a polymeric material into an extrusion system including an extruder inlet, a die outlet, and a processing space between the extruder inlet and the die outlet having a volume of less than about 25,000 cm 3 ;   forming a plurality of meltblown fibers from the polymeric material, wherein the plurality of meltblown fibers have an average diameter between about 0.1 microns and about 1.5 microns; and   forming a fiber web comprising the plurality of meltblown fibers.   
     
     
         19 - 22 . (canceled) 
     
     
         23 . A method of forming a fiber web comprising:
 introducing a polymeric material into an extrusion system including an extruder inlet, a die outlet, and a processing space between the extruder inlet and the die outlet;   processing the polymeric material in the extrusion system such that the polymeric material has a dwell time in the processing space of less than about 30 minutes and a throughput of less than about 85 lbs/hr;   forming a plurality of meltblown fibers from the polymeric material, wherein the plurality of meltblown fibers have an average diameter between about 0.1 microns and about 1.5 microns; and   forming a fiber web comprising the plurality of meltblown fibers.   
     
     
         24 - 28 . (canceled) 
     
     
         29 . A method of forming a fiber web comprising:
 introducing a polymeric material into an extrusion system including an extruder inlet, a die outlet, and a processing space between the extruder inlet and the die outlet;   processing the polymeric material in the extrusion system such that the polymeric material has a dwell time in the processing space of less than about 50 minutes and a throughput of less than about 55 lbs/hr;   forming a plurality of meltblown fibers from the polymeric material, wherein the plurality of meltblown fibers have an average diameter between about 0.1 microns and about 1.5 microns; and   forming a fiber web comprising the plurality of meltblown fibers.   
     
     
         30 - 33 . (canceled) 
     
     
         34 . The method of  claim 10 , wherein forming the plurality of meltblown fibers from the polymeric material comprises extruding the polymeric material at a die temperature between about 500° F. and about 550° F.