US Patent 7968176 Air filter material

An air filter material includes a laminate of an air inlet layer and an air outlet layer, and has a mean flow pore size of 20 μm to 40 μm, a minimum pore size of 2.4 μm to 3.8 μm, and a maximum pore size of 80 μm or less. The air inlet layer is a needle punched nonwoven fabric layer having an areal fiber weight of 55 g/m2 to 100 g/m2. The air outlet layer is a laminated spunlace nonwoven fabric made by laminating at least two or more spunlace nonwoven fabric layers having an areal fiber weight of 20 g/m2 to 60 g/m2, a mean flow pore size of 50 μm to 90 μm, a minimum pore size of 3.0 μm to 10.0 μm, and a maximum pore size of 180 μm or less.