AQUEOUS POLYTETRAFLUOROETHYLENE EMULSION AND PROCESS FOR PRODUCTION THEREOF, AQUEOUS POLYTETRAFLUOROETHYLENE DISPERSION OBTAINED USING THE EMULSION, POLYTETRAFLUOROETHYLENE FINE POWDER, AND STRETCH-EXPANDED BODY

摘要

To produce a PTFE aqueous emulsion, whereby the environmental load is little, the stability of the aqueous emulsion is high, and a molded product having high heat resistance can be obtained. A process for producing a PTFE aqueous emulsion, which comprises emulsion-polymerizing tetrafluoroethylene (TFE) by means of at least one fluorinated emulsifier selected from the group consisting of a C 4-8 fluorinated carboxylic acid having from 1 to 4 etheric oxygen atoms in its main chain, and its salts, to obtain an aqueous emulsion containing polytetrafluoroethylene (PTFE) microparticles having an average primary particle size of from 0.1 to 0.3 µm, wherein at the beginning of the emulsion polymerization of TFE, a (polyfluoroalkyl)ethylene (a) represented by "CH 2 =CH-Rf 1 ", and/or a comonomer (b) having a monomer reactivity ratio r TFE of from 0.1 to 8 in copolymerization with tetrafluoroethylene, is incorporated to the emulsion polymerization system, so as to be from 0.001 to 0.01 mass% relative to the final amount of polytetrafluoroethylene produced.