Process for preparing organic dispersion of acid type fluorinated polymer

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The organic dispersion means a dispersion of the fluorinated polymer in a hydrophilic organic medium which can contain less than 30% preferably less than 20% of water.
The hydrophilic organic medium is selected in view of the use of the organic dispersion.
Various studies for preparing a solution having high concentration and the following interest facts have been found.
The fluorinated polymers having acid type functional groups such as carboxylic acid, sulfonic acid or phosphonic acid type groups can be obtained in a form of an aqueous dispersion having high concentration by an emulsion polymerization in an aqueous medium etc.
The aqueous medium of the aqueous dispersion can be replaced to a hydrophilic organic solvent such as alcohols.
The reason is not clear, however, an organic dispersion having stable dispersibility can be obtained without any damage of the dispersion even though the aqueous medium is replaced to a hydrophilic organic solvent.
Thus, the resulting organic dispersion can be used for the fabrication of a film as the organic solvent solution.
For example, an aqueous latex of a carboxylic acid type fluorinated polymer can be separated to an aqueous medium and a latex layer having higher concentration of the polymer by a desirable centrifugal separation.
A hydrophilic organic medium is added to the concentrated latex and the centrifugal separation is repeated to decrease the content of the aqueous medium in the concentrated latex whereby the replacement to the hydrophilic organic medium is attained.
The carboxylic acid type fluorinated polymer is dispersed in the hydrophilic organic medium while maintaining the dispersion as the aqueous latex.
The organic dispersion having high concentration of the polymer as the aqueous latex can be obtained by replacement operation.
In accordance with the present invention, the organic dispersion having high concentration such as about 50 wt.
% can be easily obtained by using various kinds of hydrophilic organic media and the organic dispersion has excellent mechanical and chemical stability