| 摘要 |
PROBLEM TO BE SOLVED: To provide a new production method suitable for improvement of a PF value in a porous polytetrafluoroethylene (PTFE) film.SOLUTION: A production method comprises: a step A where a mixture that contains a polytetrafluoroethylene (PTFE) fine powder having a standard specific gravity (SSG) of 2.19 or less and a liquid lubricant is extruded into a sheet form using a flat die, thereby obtaining a PTFE sheet; a step B where the PTFE sheet is rolled along the longitudinal direction by making the PTFE sheet pass between a pair of rolls; a step C where the rolled PTFE sheet is stretched in its width direction; a step D where the liquid lubricant is removed from the PTFE sheet; and a step E where the lubricant-removed PTFE sheet is stretched in the longitudinal and width directions so that an area drawing ratio is, for example, 150-700 times, thereby making the sheet porous. |
