Multi-layer, fluid transmissive fiber structures containing nanofibers and a method of manufacturing such structures

Abstract

A multi-layer, fluid transmissive structure is provided that comprises first and second fiber layers each comprising a plurality of polymeric fibers bonded to each other at spaced apart contact points. The polymeric fibers of these fiber layers have diameters greater than one micron and collectively define interconnected interstitial spaces providing tortuous fluid flow paths through the first and second fiber layers. The structure also comprises a plurality of nanofibers disposed intermediate at least a portion of the first fiber layer and at least a portion of the second fiber layer.

What is claimed is: 
     
         1 . A method of manufacturing a multi-layer, fluid transmissive structure, the method comprising:
 providing a first fiber layer comprising a first plurality of polymeric fibers having diameters greater than one micron;   disposing a web of nanofibers on the first fiber layer;   positioning a second fiber layer over the web of nanofibers, the second fiber layer comprising a second plurality of polymeric fibers having diameters greater than one micron; and   applying heat and pressure to adhere the second fiber layer to the first fiber layer.   
     
     
         2 . A method according to  claim 1 , further comprising:
 adhering the web of nanofibers to the first fiber layer prior to positioning the second fiber layer over the web of nanofibers.   
     
     
         3 . A method according to  claim 1 , wherein the action of applying heat and pressure comprises one of the set consisting of
 calendering the combined first fiber layer, web of nanofibers and second fiber layer using a heated calender roll, and   passing the combined first fiber layer, web of nanofibers and second fiber layer through a heated die.   
     
     
         4 . A method according to  claim 1 , wherein the action of disposing a web of nanofibers on the first fiber layer includes
 forming the nanofibers by one of the set consisting of an electro-spinning process and a melt blowing process; and   forming the web of nanofibers by depositing them on the first fiber layer immediately after they are formed.   
     
     
         5 . A method according to  claim 1 , wherein the action of applying heat and pressure results in at least a portion of the second fiber layer to be bonded directly to at least a portion of the first fiber layer. 
     
     
         6 . A method according to  claim 1 , wherein the action of applying heat and pressure results in the first and second fiber layers being bonded to the web of nanofibers. 
     
     
         7 . A method according to  claim 1 , further comprising:
 disposing a second web of nanofibers on the first fiber layer; and   positioning a third fiber layer over the second web of nanofibers, the third fiber layer comprising a third plurality of polymeric fibers having diameters greater than one micron,   
       wherein the action of applying heat and pressure serves to adhere the third fiber layer to the second fiber layer. 
     
     
         8 . A multi-layer, fluid transmissive structure according to  claim 1 , wherein at least a portion of the nanofibers comprise at least one polymer material selected from the group consisting of polyvinylidene fluoride, polyamides, polyesters, polyolefins, polyurethanes, polycarbonates, and polystyrene. 
     
     
         9 . A multi-layer, fluid transmissive structure according to  claim 1 , wherein at least one of the set consisting of the first and second plurality of polymeric fibers includes fibers comprising one or more of the materials selected from the set consisting of polyethylene, low density polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate and nylon. 
     
     
         10 . A multi-layer, fluid transmissive structure according to  claim 1 , wherein the first and second fiber layers each comprise at least one of the set consisting of. woven and non-woven polymeric materials. 
     
     
         11 . A multi-layer, fluid transmissive structure according to  claim 1  wherein at least one of the set consisting of the first and second fiber layers is a bonded nonwoven fiber structure comprising a plurality of sheath-core bicomponent fibers.