FILTER MEDIUM

摘要

A filter medium for air cleaners which can prevent an oil from flying off or passing through and retains the initial dust-trapping ability for long. The filter medium (1) is composed of an upstream layer (2) comprising a nonwoven fabric obtained by superposing chemical fibers and a downstream layer (3) comprising two or more layers including nonwoven-fabric layers (4) each obtained by superposing chemical fibers by the hydro-entangling processing. The density of the upstream layer (2) is lower than the density of the downstream layer (3). The downstream layer (3) includes a natural-fiber layer (5) made of, e.g., cotton fibers, which has been interposed between any two of the nonwoven-fabric layers (4). An oil is infiltrated so as to spread in the range of from the upstream layer (2) to the natural-fiber layer (5).