| abstract |
PROBLEM TO BE SOLVED: To provide a method for producing a useful PTFE porous membrane having high collection efficiency and low pressure loss, and capable of producing a useful PTFE porous membrane with low leak of coarse particles with good reproducibility. provide. SOLUTION: A liquid lubricant is added to and mixed with polytetrafluoroethylene fine powder, and this mixture is formed into a sheet in an unfired state by at least one of an extrusion method and a rolling method, and then heated and extracted. The liquid lubricant is removed by at least one of the methods. This sheet-like molded body is stretched in the longitudinal direction, has an endothermic peak in a temperature range of 345 ± 5 ° C. on a crystal melting curve by a differential scanning calorimeter, and has a crystal conversion of 0.1 to 0.85; A sheet-like polytetrafluoroethylene molded article having a specific gravity of 1.4 or less is produced. This is stretched in the width direction to produce a polytetrafluoroethylene porous membrane. |