TECHNOLOGY FOCUS - POLYMERS - Preferred Polymer: The fibrilliform fluorocarbon polymer is a polytetrafluoroethylene or a copolymer comprising at least 95 mol % of polymerization units derived from tetrafluoroethylene. The ion exchange polymer dispersion contains 0.5-15 mass % of fibrilliform fluorocarbon polymer. The ion exchange polymer is a fluorinated polymer with sulfonic acid groups which consists of polymerization units derived from tetrafluoroethylene and polymerization units derived from CF2=CF(OCF2CFX)m-Op-(CF2)nSO3HX = fluorine atom or trifluoromethyl group;m = 0-3;n = 0-12;p = 0 or 1 provided that when n is 0, p is also 0;Preferred Process: The temperature of the dispersion medium is maintained in the temperature range from room temperature to 270 degrees C, during dispersion. Alternately, the production of polymer dispersion comprises mixing a solution or dispersion of a polymer containing sulfonic acid groups and a dispersion of a fluorocarbon polymer and applying a shearing force to the solution or dispersion to fibrillate the fluorocarbon polymer. EXAMPLE - A powdery copolymer consisting of polymerization units derived from tetrafluoroethylene and polymerization units derived from CF2=CF-OCF2CF(CF3)O(CF2)2SO2F, was hydrolyzed, converted to the acid form and dispersed in ethanol at a concentration of 9 mass %, and the resulting dispersion concentrated to a solid content of 11.6 mass %. The obtained dispersion (11 g) and Aflon AD1 (RTM: polytetrafluoroethylene) (0.25 g) were mixed and dispersed in a homogenizer at a rotational speed of 25000 RPM for 10 minutes to apply a shearing force to promote fibrillation by applying a shearing force to the polytetrafluoroethylene dispersion. An ion exchange polymer dispersion containing a fibrilliform fluorocarbon polymer which comprises a fibrilliform fluorocarbon polymer and a perfluorocarbon polymer containing sulfonic acid groups was obtained. The ion exchange polymer dispersion was cast on a polyethylene terephthalate film with a silicone release agent treated surface to form an ion exchange membrane. The specific resistance and tear strength of the fibril-containing ion exchange membrane were measured and found to be 4 O.cm and 3 N/mm, respectively.