Filter medium for air filters

摘要

A filter medium for air filters wherein the collection performance of polytetrafluoroethylene (PTFE) membranes is not damaged even after processing, for example, pleating and bonding to air-permeable supporting members. The filter medium containing a laminate (2) containing at least three layers of porous PTFE membranes wherein the pressure drop of a porous PTFE membrane (4) located as an outermost layer has a pressure drop of 1/2 times or less the pressure drop of porous PTFE membrane (5) located as at least one intermediate layer. Air-permeable supporting members (3) are bonded to both outermost layers of the laminate (4) to obtain a filter medium for air filters (1).