| 摘要 |
PROBLEM TO BE SOLVED: To provide a high performance filter medium enabling easy discarding disposal of waste, wherein capturing capacity is prevented from being lowered for a long time by bonding a fiber web made by mixing very thin organic fibers and heat-fusible fibers respectively having mean fiber diameters of particular values by heat-fusible fibers. SOLUTION: A filter medium used for this filter unit preferably contains 50-90 wt.% of very thin organic fibers having a mean fiber diameter of less than 1μm and prepared by a melt blow method and 50-10 wt.% of heat-fusible fibers having a mean fiber diameter of 5-100μm. And a fiber web prepared by mixing the very thin organic fibers and the heat-fusible fibers are preferably subjected to a pressure treatment at a temperature of a melting point of a low melting point component contained in the heat-fusible fibers or lower. Or, the web prepared by mixing the very thin organic fibers and the heat-fusible fibers is preferably subjected to a heating treatment without substantially applying pressure at a temperature above a melting point of the low melting point component contained in the heat-fusible fibers and lower than a melting point of the very thin organic fibers.
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