To enhance the cleanness of an environment in a clean room using the original properties of a porous film of a polytetrafluoroethylene(PTFE) by forming a filter medium for a filter of a laminate containing an ultra high molecular weight polyolefin porous film and a PTFE porous film.
The filter medium 1 for a filter is formed by laminating at least one layer of a PTFE porous film 2 and at least one layer of an ultra high molecular weight polyolefin porous film 3. In addition, the degree of dust generation by a tear and rub test is set at 500 pcs/cf or less. In addition, the amount of either one selected from chemical compounds such as DOP, BHT or DBP quantitatively determined by gas chromatography is set at 2 μg/g or less (2 ppm or less). Further, an ultra high molecular weight polyethylene porous film is adopted as the ultra high molecular weight polyolefin porous film 3. Alternatively, a film of a porous structure formed of voids among the connected particles of the ultra high molecular weight polyolefin is adopted.
NAGAI YOZO
KAWANO EIZO
MAEOKA TAKUYA
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