Patent ID: 7094838

Claim:
A method for producing a fluorine-containing polymer powder comprising the steps of: mixing fluorine-containing polymer powder A which has not been treated with a fluorinating agent with fluorine-containing polymer powder B, which is prepared by contacting fluorine-containing polymer powder A with a fluorinating agent so that the total number of —CH 2 OH and —COF terminal groups is decreased to 25 or less per 10 6 carbon atoms, to obtain a mixture of fluorine-containing polymer powders having 7 to 50 of —COOH, —COOCH 3 , —CH 2 OH and —COF terminal groups per 10 6 carbon atoms, increasing a density of the fluorine-containing polymer powder so that a specific gravity reaches at least 90% of the true specific gravity of the fluorine-containing polymer, milling the mixture, air classifying the milled mixture to remove fine particles and fibrous particles in an amount of 30 to 40% of the whole particle size distribution of the milled mixture, and classifying the residual mixture to remove coarse particles in an amount of 1 to 20% of the whole particle size distribution.