METHOD FOR CONCENTRATING AQUEOUS EMULSION OF FLUOROPOLYMER

摘要

PURPOSE:To concentrate an aqueous emulsion of a fluoropolymer with a small amount of a surfactant without aggregating polymer particles by transferring water from the aqueous emulsion of a fluoropolymer separated by ion exchange membranes to aqueous solutions of electrolytes. CONSTITUTION:An aqueous emulsion of a fluoropolymer exists in one zone of a device which has at least two zones for holding materials mutually separated by ion exchange membranes and an aqueous solution of an electrolyte exists in other zone. Water in the aqueous emulsion of the fluoropolymer is transferred through the ion exchange membranes to the zone of the solution of the electrolyte to concentrate the aqueous emulsion of the fluoropolymer. One of the ion exchange membranes is a cation exchange membrane and the electrolyte is an acid or a salt. The other ion exchange membrane is an anion exchange membrane and the electrolyte is a base or its salt. The acid (salt) electrolyte separated by the cationic exchange membrane exists in one side and the base (salt) electrolyte separated by the anionic exchange membrane, exists in the other side so as to sandwich the aqueous emulsion of the fluoropolymer in-between to provide the objective concentrating method. The exchange membrane is a filmy membrane or a tubular membrane.