PROCESS FOR PRODUCING PURIFIED POLYTETRAFLUOROETHYLENE AQUEOUS-DISPERSION

摘要

A process for producing a purified polytetrafluoroethylene aqueous-dispersion, comprising passing a crude PTFE aqueous-dispersion containing 10 to 50 mass% of polytetrafluoroethylene (PTFE) microparticles of 0.1 to 0.5 µm average diameter, 0.05 to 1.0 mass%, based on the mass of PTFE, of fluorocarboxylic acid salt (APFO) and 2 to 20 mass%, based on the mass of PTFE, of nonionic surfactant through a column packed with weakly basic AER upward from bottom at a linear velocity of 0.1 to 2 m/sec so that the contact time with the weakly basic AER is in the range of 0.2 to 4 hr to thereby lower the concentration of APFO. In this process, the amount of APFO absorbed in the anion exchange resin can be increased, and PTFE aggregation during the passage can be prevented. Further, elution of absorbed APFO is easy.