Aqueous polytetrafluoroethylene emulsion, polytetrafluoroethylene fine powder and porous material obtained therefrom
View Patent ↗To provide an aqueous polytetrafluoroethylene (PTFE) emulsion which does not substantially contain ammonium perfluorooctanoate, and which is obtained by emulsion polymerization. Further, to provide a PTFE fine powder which is obtained from the aqueous PTFE emulsion and is excellent in a paste extrusion processability, and a porous material. An aqueous polytetrafluoroethylene emulsion obtained by carrying out emulsion polymerization of tetrafluoroethylene alone or together with another copolymerizable monomer in an aqueous medium, wherein a fluorinated emulsifier of the formula (1): CF 2 CF 2 (O)mCF 2 CF 2 OCF 2 COOA wherein X is a hydrogen atom or a fluorine atom, A is a hydrogen atom, an alkali metal or NH4, and m is an integer of 0 or i, is used in an amount of from 1,500 to 20,000 ppm, based on the final yield of polytetrafluoroethylene.
1. A polytetrafluoroethylene fine powder obtained by coagulating an aqueous polytetrafluoroethylene emulsion obtained by carrying out emulsion polymerization of tetrafluoroethylene alone or together with another copolymerizable monomer in an aqueous medium, wherein
a fluorinated emulsifier of the formula:
XCF 2 CF 2 (O) m CF 2 CF 2 OCF 2 COOA
wherein X is a hydrogen atom or a fluorine atom, A is a hydrogen atom, an alkali metal or NH 4 , and m is an integer of 0 or 1,
is used in an amount of from 1,500 to 20,000 ppm, based on the final yield of polytetrafluoroethylene.
2. The polytetrafluoroethylene fine powder according to claim 1 , which has a standard specific gravity of from 2.14 to 2.20.
3. A porous material of polytetrafluoroethylene obtained by paste extrusion of the polytetrafluoroethylene fine powder as defined in claim 1 , followed by stretching.