Patent ID: 8372292

Claim:
A method of making a polymeric filtration medium, comprising: melting a polymer having a molecular weight distribution (M w /M n ) between about 1.4 and about 6 and a melt flow rate greater than about 1000 g/10 minutes to provide molten polymer; extruding the molten polymer through a plurality of orifices in a die to form continuous primary filaments of polymer; attenuating the continuous primary filaments with an air stream to form discrete melt blown fibers of polymer; cooling the fibers; and collecting the fibers to form at least one fibrous mat of randomly oriented polymeric fibers, and wherein the polymeric fibers have an average diameter between about 0.7 μm and about 2.5 μm and between about 20% and about 80% of the polymeric fibers have a diameter ≦1 μm.