Patent ID: 7594946

Claim:
An air-cleaner filter material for an internal combustion engine, which comprises (a) a dust-collecting layer comprising a melt-blown nonwoven fabric having a maximum pore size of 100 μm or less, which is sufficient to remove dust introduced into the air by an internal-combustion engine, and (b) a dust-retaining layer comprising a thermal-bond nonwoven fabric (i) comprising two or more webs comprising fibers with a core/sheath structure and different fiber diameters of 10 μm to 80 μm, wherein the webs are arranged in the order of increasing the proportion of smaller fiber diameter in the direction from the upstream to downstream side, and wherein the webs are thermally contact-bonded to a predetermined thickness, and (ii) having an average fiber diameter of 30 μm to 60 μm and a fiber areal weight of 80 to 300 g/m 2 , which fiber areal weight decreases in the direction from the upstream to downstream side, wherein the dust-retaining layer is arranged upstream of the dust-collecting layer and laminated integrally by heat fusion with the dust-collecting layer, and wherein the in-plane of the filter material has portions of high and low fiber density, and the portion of high fiber density occurs in a lattice pattern.