FILTER MEDIUM, ITS MANUFACTURING METHOD, AND CARTRIDGE FILTER

PROBLEM TO BE SOLVED: To provide a high collection capacity and a long service life by providing features to fiber assembly constituting a filter medium removing foreign matter from fluid. SOLUTION: The filter medium is formed by laminating at least two or more layers of nonwoven fabric, a first nonwoven fabric at an inlet side of the fluid has a density of 0.05-0.5 g/cm3, an average hole diameter of 5-35 μm, and a second nonwoven fabric at an outlet side of the fluid is melt-blown nonwoven fabric with at least one face smoothed. The smoothed face is disposed in the outlet side, the melt-blown nonwoven fabric has a density of 0.15-0.7 g/cm3, an average hole diameter of 0.5-20 μm, a maximum hole diameter of 5-30 μm, and a ratio of the average hole diameter of the first nonwoven fabric to the maximum hole diameter of the second nonwoven fabric is 0.5-5 times. The cartridge filter using the filter medium has a high collection accuracy, and demonstrates a long service life even in filtration of fluid mixed with gel-like foreign matter. COPYRIGHT: (C)2009,JPO&INPIT