Filter medium equipped with porous film, method of manufacturing same, filter pack, and filter unit
A filter medium includes a porous film and a support material supporting the porous film. The porous film includes polytetrafluoroethylene, has an average pore diameter of at least 2.5 μm, and has a porosity of at least 95%. A pressure loss is less than 100 Pa when air is passed through the filter medium at a velocity of 5.3 cm/sec. A collection efficiency of NaCl particles is at least 95% when air including NaCl particles with a particle diameter of 0.3 μm is passed through the filter medium at a velocity of 5.3 cm/sec. A PF value is at least 30, where PF={−log [(100−collection efficiency (%))/100]/pressure loss (Pa)}×1000. A dust holding capacity of polyalphaolefin particles held in the filter medium is at least 15 g/m 2 when air including polyalphaolefin particles with a count median diameter of 0.25 μm is continuously passed through the filter medium at a velocity of 5.3 cm/sec and pressure loss reaches 300 Pa.
1. A filter medium comprising:
a porous film including polytetrafluoroethylene, having an average pore diameter of at least 2.5 μm, and having a porosity of at least 95%; and
a support material supporting the porous film,
a pressure loss being less than 100 Pa when air is passed through the filter medium at a velocity of 5.3 cm/sec,
a collection efficiency of NaCl particles being at least 95% when air including NaCl particles with a particle diameter of 0.3 μm is passed through the filter medium at a velocity of 5.3 cm/sec,
a PF value being at least 30, where PF={−log [(100−collection efficiency (%))/100]/pressure loss (Pa)}×1000, and
a dust holding capacity of polyalphaolefin particles held in the filter medium being at least 15 g/m 2 when air including polyalphaolefin particles with a count median diameter of 0.25 μm is continuously passed through the filter medium at a velocity of 5.3 cm/sec and pressure loss reaches 300 Pa.
2. The filter medium according to claim 1 , wherein
the porous film mainly includes modified polytetrafluoroethylene.
3. The filter medium according to claim 2 , wherein
the modified polytetrafluoroethylene is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether.
4. A filter pack including the filter medium according to claim 1 , the filter medium being shaped into a predetermined shape.
5. A filter unit including e filter pack according to claim 4 , the filter unit further comprising
a frame body in which the filter pack is stored.