Patent ID: 7238735
Filing Date: 2007-07-03
Classification: C08F

Abstract:
1. A process for producing an aqueous dispersion of purified polytetrafluoroethylene, which comprises passing a crude aqueous dispersion of polytetrafluoroethylene comprising from 10 to 50 mass % of polytetrafluoroethylene fine particles having an average particle diameter of from 0.1 to 0.5 μm, from 0.05 to 1.0 mass %, based on polytetrafluoroethylene, of a fluorine-containing carboxylic acid salt represented by the formula (1) and from 2 to 20 mass %, based on polytetrafluoroethylene, of a nonionic surfactant represented by the formula (2) and/or the formula (3) through a column packed with a weak basic anion exchange resin upward at a linear velocity of 0.1 to 2 mm/sec with a contact time of 0.2 to 4 hours to reduce the content of the fluorine-containing carboxylic acid salt: formula (1): R formula (2): R formula (3): R