Patent ID: 8021457

Claim:
A filter medium comprising: two layers, the layers consisting essentially of, a loading layer adjacent to an efficiency layer, the efficiency layer having a mean flow pore size smaller than the loading layer, the loading layer consisting essentially of a blend of: about 5% to 50 wt % of a bicomponent binder fiber, about 50 to 95 wt % of a media fiber consisting of a glass fiber, and about 0.5 to 25 wt % of a binder resin, wherein the loading layer has a basis weight of about 30 to 250 g-m −2 and wherein the loading layer provides a permeability of 10 to 40 ft-min −1 , and a wet bursting strength of 5 to 50 lb-in −2 , inclusive; and the efficiency layer consisting essentially of a blend of, about 5% to 50 wt % of a bicomponent binder fiber, about 50 to 95 wt % of a media fiber consisting of a glass fiber, and about 0.5 to 25 wt % of a binder resin, wherein the efficiency layer has a basis weight of about 30 to 250 g-m −2 and wherein the efficiency layer provides a permeability of 10 to 40 ft-min −1 , and a wet bursting strength of 5 to 50 lb-in −2 , inclusive.