| 摘要 |
PROBLEM TO BE SOLVED: To obtain a PTFE porous film having a high PF value even in relatively high thickness. SOLUTION: The method for producing a PTFE porous film comprises a process for a processing a mixture composed of a thermally expandable microcapsule obtained by sealing a volatile blowing agent having a boiling point lower than the softening point of a thermoplastic resin in a shell containing the thermoplastic resin and polytetrafluoroethylene fine powder into a sheetlike material and stretching the sheetlike material at least in the uniaxial direction at a temperature lower than the softening point of the thermoplastic resin. In the process, after the sheetlike material is obtained, the thermally expandable microcapsule is heated at a temperature equal to or higher than the boiling point of the volatile blowing agent and lower than the softening point of the thermoplastic resin to expand the shell. COPYRIGHT: (C)2007,JPO&INPIT
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