Oleophobic filter materials for filter venting applications

Abstract

Oleophobic and hydrophobic filters for filter venting applications are made by forming a polydimethylsiloxane coating on the surface of a filtration substrate. The filters have high water penetration pressures and high air permeabilities. The coatings are formed by polymerizing vinyl terminated siloxane with a crosslinker such as hydrosilicone in the presence of a catalyst. Alternatively, the coatings can be formed by heat curing after exposing the substrate to methyl silicone and crosslinking at high temperature.

What is claimed is:  
     
         1 . A vent filter for a medical device, the vent filter comprising an oleophobic, hydrophobic, coated porous polymeric membrane, the membrane having an air permeability, the coated filter further comprising a coating derived from a coating formulation, wherein the coating is permanently crosslinked to the membrane, and wherein the coating formulation comprises a vinyl-terminated siloxane polymer, wherein the vent filter may be steam sterilized or chemically sterilized without substantial loss of air permeability.  
     
     
         2 . The filter of  claim 1 , wherein the porous polymeric membrane comprises an asymmetric membrane.  
     
     
         3 . The filter of  claim 1 , wherein the porous polymeric membrane comprises an isotropic membrane.  
     
     
         4 . The filter of  claim 1 , wherein the vinyl-terminated siloxane polymer comprises a vinyl-terminated fluorosiloxane polymer.  
     
     
         5 . The filter of  claim 1 , wherein the siloxane polymer comprises a vinyldimethyl-terminated siloxane.  
     
     
         6 . A method of producing a vent filter for a medical device comprising a hydrophobic, oleophobic filter, comprising the steps of: 
 providing a porous polymeric membrane;    contacting the membrane with a coating formulation comprising a vinyl-terminated siloxane polymer to produce a coated filter;    crosslinking the coating formulation to the filter;    recovering an oleophobic, hydrophobic, permanently coated filter having an air permeability; and    incorporating the oleophobic, hydrophobic permanently coated filter into a vent filter for a medical device, wherein the vent filter may be steam sterilized or chemically sterilized without substantial loss of air permeability.    
     
     
         7 . The method of  claim 6 , wherein the porous polymeric membrane comprises an asymmetric membrane.  
     
     
         8 . The method of  claim 6 , wherein the porous polymeric membrane comprises an isotropic membrane.  
     
     
         9 . The method of  claim 6 , wherein the vinyl-terminated siloxane polymer comprises a vinyl-terminated fluorosiloxane polymer.  
     
     
         10 . The method of  claim 6 , wherein the siloxane polymer comprises a vinyldimethyl-terminated siloxane.