Polytetrafluoroethylene synthesis method
2021-08-03
Industrially, it is produced by suspension polymerization or emulsion polymerization.
1. Preparation of monomer tetrafluoroethylene
Industrially, trichloromethane is used as raw material, and trichloromethane is fluorinated with anhydrous hydrofluoric acid. The reaction temperature is above 65ºC. Antimony pentachloride is used as a catalyst. Finally, tetrafluoroethylene is made by thermal cracking. Zinc can also be used with tetrafluorodichloroethane at high temperature to produce tetrafluoroethylene.
2. Preparation of polytetrafluoroethylene
In an enamel or stainless steel polymerizer, use water as the medium, potassium persulfate as the initiator, perfluorocarboxylic ammonium salt as the dispersant, fluorocarbon as the stabilizer, and tetrafluoroethylene through redox polymerization to produce polytetrafluoroethylene. Vinyl.
Add various additives into the reaction kettle, the tetrafluoroethylene monomer enters the polymerization kettle in the gaseous phase, adjust the temperature in the kettle to 25°C, and then add a certain amount of activator (sodium bisulfite) to initiate polymerization through an oxidation-reduction system. Continuously add monomers during the polymerization process and keep the polymerization pressure 0.49~0.78MPa. The dispersion obtained after polymerization is diluted with water to a certain concentration, and the temperature is adjusted to 15~20ºC. After condensing with mechanical stirring, it is washed and dried with water. This product is a fine-grained resin.
