Filtration media for liquid filtration

Abstract

Filtration media including at least one layer of nanofibers having average diameters less than 1000 nanometers with optional scrim layer(s) are disclosed for filtering particulate matter in liquid. The media achieve flow rates of at least 0.055 L/min/cm 2 at relatively high levels of solidity. The media have also advantageously been found to have non-diminishing flow rates as differential pressures increase between 2 psi (14 kPa) and 15 psi (100 kPa).

1 . A filtration medium comprising at least one nanofiber layer of polymeric nanofibers wherein the nanofibers have average fiber diameters of less than about 1 μm and the nanofiber layer has a mean flow pore size of between about 0.5 μm and about 5.0 μm, a solidity of between about 15 vol % and about 90 vol % and a liquid flow rate through the medium of at least about 0.055 L/min/cm 2  of water at 10 psi (69 kPa) differential pressure, wherein the filtration medium consists solely of nanofibers. 
   
   
       2 . The filtration medium of  claim 1  wherein the solidity is between about 30 vol % and about 70 vol %. 
   
   
       3 . The filtration medium of  claim 1  wherein the filtration medium has a thickness of between about 10 μm and about 600 μm. 
   
   
       4 . The filtration medium of  claim 1  wherein the nanofiber layer has a basis weight of between about 2 g/m 2  and about 100 g/m 2 . 
   
   
       5 . The filtration medium of  claim 1  wherein the ratio of the change in liquid flow rate through the medium to the corresponding change in differential pressure across the medium is positive at a differential pressure in the range between 2 psi (14 kPa) and 15 psi (100 kPa). 
   
   
       6 . The filtration medium of  claim 1  further comprising a supporting scrim layer. 
   
   
       7 . The filtration medium of  claim 6  wherein the supporting scrim layer is selected from the group consisting of spunbonded nonwovens, meltblown nonwovens, needle punched nonwovens, spunlaced nonwovens, wet laid nonwovens, resin-bonded nonwovens, woven fabrics, knit fabrics, apertured films, paper, and combinations thereof. 
   
   
       8 . The filtration medium of  claim 1  wherein the nanofibers have average fiber diameters of about 0.10 μm to about 1 μm. 
   
   
       9 . The filtration medium of  claim 1  wherein the polymeric nanofibers comprise a polymer selected from the group consisting of polyimide, aliphatic polyamide, aromatic polyamide, polysulfone, cellulose acetate, polyether sulfone, polyurethane, poly(urea urethane), polybenzimidazole, polyetherimide, polyacrylonitrile, poly(ethylene terephthalate), polypropylene, polyaniline, poly(ethylene oxide), poly(ethylene naphthalate), poly(butylene terephthalate), styrene butadiene rubber, polystyrene, poly(vinyl chloride), poly(vinyl alcohol), poly(vinylidene fluoride), poly(vinyl butylene) and copolymers or derivative compounds thereof. 
   
   
       10 - 11 . (canceled) 
   
   
       12 . A filter comprising a filtration medium having at least one nanofiber layer of polymeric nanofibers wherein the nanofibers have average fiber diameters of less than about 1 μm and the nanofiber layer has a mean flow pore size of between about 0.5 μm and about 5.0 μm, a solidity of between about 15 vol % and about 90 vol % and a liquid flow rate through the medium of at least about 0.055 L/min/cm 2  of water at 10 psi (69 kPa) differential pressure, wherein the filtration medium consists solely of nanofibers. 
   
   
       13 . (canceled) 
   
   
       14 . A filtration medium comprising at least one nanofiber layer of polymeric nanofibers wherein the nanofibers have average fiber diameters of less than about 1 μm and the nanofiber layer has a mean flow pore size of between about 0.5 μm and about 5.0 μm, a solidity of between about 15 vol % and about 90 vol %, a liquid flow rate through the medium of at least about 0.055 L/min/cm 2  of water at 10 psi (69 kPa) differential pressure, and a basis weight of at least about 5 g/m 2 . 
   
   
       15 . The filtration medium of  claim 14  wherein the nanofiber layer has a basis weight of between about 10 g/m 2  and about 90 g/m 2 . 
   
   
       16 . A filter comprising a filtration medium having at least one nanofiber layer of polymeric nanofibers wherein the nanofibers have average fiber diameters of less than about 1 μm and the nanofiber layer has a mean flow pore size of between about 0.5 μm and about 5.0 μm, a solidity of between about 15 vol % and about 90 vol %, a liquid flow rate through the medium of at least about 0.055 L/min/cm 2  of water at 10 psi (69 kPa) differential pressure, and a basis weight of at least about 5 g/m 2 .