Patent ID: 7687416

Claim:
A mat of fibrous filter media comprising a downstream side having at least a first portion of meltblown fibers of selected fiber diameter and an upstream side having at least a second portion of meltblown fibers also of selected fiber diameter, said first portion of meltblown fibers and said second portion of meltblown fibers being continuously intermingled along a planar interface between said first portion and said second portion, said first portion and said second portion being formed of a single material, said first portion being formed of generally straight and substantially aligned fibers of a first selected porosity and said second portion being of substantially curled fibers of a second selected larger porosity than said first portion, at least one of said first and second portion of meltblown fibers having a fiber diameter of between about 0.3 microns and about 25 microns, wherein said mat of fibrous filter media has a fiber size gradient and gradient density and porosity through a depth dimension transverse to said planar interface.