| 摘要 |
PROBLEM TO BE SOLVED: To provide a filter medium having closed cells hard to be damaged and not permitting the penetration of water; and a method for manufacturing the filter medium.SOLUTION: A filter medium 12 molded into a cross pillar shape from polyolefinic foam having a closed-cell structure is constituted so as to include a skin layer at least at a part of the surface. Further, a polyolefinic foam sheet having the closed-cell structure having skin layers on both surfaces thereof by an extrusion foaming method or a mold foaming method and the foam sheet is punched in the cross shape to manufacture the filter medium. Furthermore, the long polyolefinic foam formed into a cross shape in its cross-sectional shape and comprising the closed-cell structure having skin layers on the surfaces other than end surfaces thereof is molded by an extrusion foaming method and cut to manufacture the filter medium. By this constitution, at least a part of the surface of the filter medium is covered with the relatively strong skin layers to suppress the damage of the closed cells and the penetration of water into the closed cells. |
