Non-Woven Polymeric Webs

Abstract

A non-woven web, comprising one or more polymeric fibers, wherein the number-average fiber diameter distribution of said one or more polymeric fibers conforms to a Johnson unbounded distribution. Non-woven webs comprising such polymeric fibers are rendered with mean-flow pore size and porosity desirable for specific filtration applications such as hepafiltration.

We claim: 
     
         1 . A non-woven web, comprising one or more polymeric fibers, wherein said one or more polymeric fibers have a number-average fiber diameter distribution that conforms to a Johnson unbounded distribution. 
     
     
         2 . The non-woven web as recited in  claim 1 , wherein said one or more polymeric fibers are produced from the same spinning head. 
     
     
         3 . The non-woven web as recited in  claim 1 , wherein the number-average mean fiber size of said one or more polymeric fibers is less than 1,000 nm. 
     
     
         4 . The non-woven web as recited in  claim 1 , wherein said non-woven web has a Frazier porosity in the range of from about 5 ft 3 .ft- 2 min −1  (0.0254 m 3 .m −2 .sec −1 ) to about 100 ft 3 .ft- 2 min −1  (0.508 m 3 .m −2 .sec −1 ) at a basis weight of approximately 25 g.m −2 . 
     
     
         5 . The non-woven web as recited in  claim 1 , wherein said non-woven web flux barrier properties is greater than 0.01 at a basis weight of ˜25 g.m −2 . 
     
     
         6 . A non-woven web, comprising one or more fibers, wherein said non-woven web is prepared by a method comprising the steps of:
 (i) supplying a spinning melt or solution of at least one thermoplastic polymer to an inner spinning surface of a rotating distribution disc having a forward-surface, fiber-discharge edge;   (ii) issuing said spinning melt or solution along said inner spinning surface of said rotating distribution disc so as to distribute said spinning melt or solution into a thin film and toward the forward-surface, fiber-discharge edge; and   (iii) discharging separate molten or solution polymer fiber streams from said forward-surface, discharge-edge into a gas stream to attenuate the fiber stream to produce polymeric fibers that have a mean fiber diameter less than about 1,000 nm;   
       wherein said polymer melt or solution has a viscosity that is above a minimum effective viscosity for producing said polymeric fibers with the number-average fiber diameter distribution of said polymeric fibers conforms to a Johnson unbounded distribution; and/or 
       wherein said polymer melt or solution has a flow-rate that is below a maximum effective flow-rate for producing said polymeric fibers with the number-average fiber diameter distribution of said polymeric fibers conforms to a Johnson unbounded distribution; and/or 
       wherein said polymer solution has a concentration that is above a minimum effective concentration for producing said polymeric fibers with the number-average fiber diameter distribution of said polymeric fibers conforms to a Johnson unbounded distribution; and/or 
       wherein the rotational speed of said rotating distribution disc is below a maximum effective rotational speed for producing said polymeric fibers with the number-average fiber diameter distribution of said polymeric fibers conforms to a Johnson unbounded distribution.