Patent ID: 6261979
Filing Date: 2001-07-17
Classification: B01D,B29C,B29K,Y10T

Abstract:
A filter medium comprising a polytetrafluoroethylene porous membrane, wherein an average pore diameter of the polytetrafluoroethylene porous membrane is more than 0.5 .mu.m and exhibits a pressure loss when air is passed through the medium at a flow velocity of 5.3 cm/sec is from 2 to 50 mmH.sub.2 O, and a PF value calculated from the pressure loss and a collection efficiency using dioctylphthalate of a particle size of 0.10 to 0.12 .mu.m according to an equation (1) below is between 18 and 22 (Equation (1) ##EQU3##Permeability (%)=100-Collection Efficiency (%).