Produits Chimiques Ugine Kuhlmann

Jean-Louis Herisson

Jean Blaise

The process for the polymerization in aqueous dispersion of tetrafluoroethylene in the presence of an emulsifier and an initiator, with the latter yielding free radicals between 0.degree. and 45.degree. C. and being destroyed for a temperature above 45.degree. C., characterized by the fact that the temperature of the reaction medium as a function of polymerization time is made to follow an ascending curve, Temperature .degree.C. versus t (time in minutes) whose slope (.DELTA.T/.DELTA.t) cannot be less than 1/6, .DELTA.T representing the temperature in .degree.C. at a given time in minutes .DELTA.t, with this ascending curve being situated inside of a sector limited by two straight lines y=(7/12)x and y=(15/7)x+45, in which y and x respectively represent the temperature in .degree.C. and the time expressed in minutes, and by the fact that the initiator is destroyed before the concentration of polytetrafluoroethylene in the dispersion has reached 20%.

Process for the polymerization of tetrafluoroethylene in aqueous

A treatment procedure for aqueous colloidal polytetrafluoroethylene dispersions obtained by polymerization of tetrafluoroethylene in the presence of the lithium salt of a perfluoroalkanesulfonic acid as the emulsifier, characterized by the fact that a basic hydroxide or a soluble ammonium, alkali metal or alkaline-earth salt, with the exception of lithium hydroxide or a lithium salt, is added to the dispersion.

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Brignais, France

Jean-Louis Herisson