PROCESS FOR PRODUCING AN AQUEOUS POLYTETRAFLUOROETHYLENE EMULSION, AND POLYTETRAFLUOROETHYLENE FINE POWDER AND POROUS MATERIAL PRODUCED FROM THE SAME

摘要

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):
€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒXCF 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.