FILTER MEDIUM FOR AIR FILTER, FILTER PACK, AIR FILTER UNIT, AND METHOD FOR MANUFACTURING FILTER MEDIUM FOR AIR FILTER

摘要

Provided are a filter medium for an air filter that greatly improves the amount of dust retention while maintaining high collection efficiency, a filter pack, an air filter unit, and a method for manufacturing a filter medium for an air filter. This filter medium for an air filter is provided with a first porous membrane and a second porous membrane formed from a fluorine resin. The second porous membrane is disposed more on the downstream side of airflow than the first porous membrane. The first porous membrane has a polyalphaolefin particle retention rate greater than the second porous membrane when air that includes polyalphaolefin particles with a median diameter of 0.25 µm is continuously passed through at a flow rate of 5.3 cm/sec with a pressure loss raised by 250 Pa. The filter medium for an air filter is characterized by having a pressure loss of less than 200 Pa, a collection efficiency for NaCl particles with a diameter of 0.3 µm of 99.97% or greater, and a retention rate for polyalphaolefin particles with a median diameter of 0.25 µm of 25 g/m2 or greater.