MEDIUM FOR MID-PERFORMANCE AIR FILTER, PROCESS FOR PRODUCING THE SAME AND MID-PERFORMANCE AIR FILTER

摘要

A medium for mid-performance air filter that ensures the passage of air by means of voids within a sheet constituting the filter medium, and that without trapping dust disproportionately on its air inlet side, is capable of trapping dust uniformly in the direction of thickness of the filter medium, and that accordingly is capable of prolonging its service life; a process for producing the same; and a mid-performance air filter. There is provided a medium for mid-performance air filter, comprising a sheet having voids formed by causing fragments resulting from bursting of expandable particles to bond surrounding fibers, characterized in that the sheet is composed of 70 to 90 mass% of glass staple fibers of 2 to 8 mum average fiber diameter, 0 to 15 mass% of glass staple fibers of < 2 mum average fiber diameter, 5 to 15 mass% of sticky synthetic fibers of 10 to 35 mum average fiber diameter and 3 to 10 mass% of fragments from expandable particles.