Process for preparing emulsion polymers of fluoro-olefins

An improved process for preparing emulsion polymers of fluoro-olefins is provided. A fluorine containing polymer powder exhibiting excellent paste extrusion properties (a nearly spherical shape and of considerable size) can be prepared by irradiating a fluoro-olefin monomer with ionizing radiation (1 x 103 to 5 x 105 R/hr) in a water emulsion system at a reaction pressure of 10 to 25 kg/cm2 and at a temperature of 10 to 500C, under the following conditions: S (gas-liquid interfacial area)/V (volume of aqueous medium) <=0.04 cm-1; v (circulating velocity of the tip of a screw stirrer) 0.5 to 5 m/sec; kla (relative volume coeff., defined by the following equation) ΔC/(2Δt)=kla x C wherein C is the solubility of O2 in water and ΔC/Δt is the decreasing velocity of sulfite concentration when a 1 to 2 g-mol/liter solution of sodium sulfite is stirred in atmospheric air under the same conditions as in the polymerization. In one example, C2F4 was emulsion-polymerized under the following conditions: pressure 20 kg/cm2; temp. 200C; S/V 0.023 cm-1; v 1.2 m/sec; kla 2.8 hr-1. In 13.5 hrs, a latex of polymer content 35% by wt. was obtained. Polymer yield was 99.5%. (Kaichi, S.)