METHOD OF MANUFACTURING POLYTETRAFLUOROETHYLENE POROUS MEMBRANE AND FILTER MEDIUM FOR FILTER , AND FILTER UNIT

摘要

PROBLEM TO BE SOLVED: To provide a method of manufacturing a polytetrafluoroethylene (PTFE) porous membrane in which high catching efficiency and low pressure loss are made compatible even while an average bore size is made larger and a membrane thickness is made thicker than a conventional PTFE porous membrane.

SOLUTION: In the method of manufacturing the PTFE porous membrane, a non-calcined polytetrafluoroethylene sheet is stretched for 5 to 30 times in a prescribed direction at a temperature equal to or higher than the fusion point of polytetrafluoroethylene, and the stretched sheet is stretched further for 5 to 40 times in a direction different from the prescribed direction at a temperature below the fusion point and then is heated to the temperature equal to or higher than the fusion point.

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