US Patent 7407703 Composite membrane having oleophobic properties

An air permeable composite article that in one embodiment includes a porous base membrane that includes a plurality of nodes and fibrils defining a plurality of interconnecting pores extending through the porous base membrane with each node and fibril having a surface. The composite article also includes a precipitated coating material deposited on the surfaces of the plurality of nodes and fibrils. The coating material includes a copolymer formed from a fluorinated acrylate or methacrylate, an n-alkyl acrylate or methacrylate, and an isocyanate crosslinker. The precipitated coating material provides oil and contaminating agent resistance of at least a number six measured in accordance with AATCC 118 test method.