| 摘要 |
PROBLEM TO BE SOLVED: To obtain a granular powder having excellent powder flow by granulating a polytetrafluoroethylene having a specified particle size under agitation in water in the presence of an organic liquid which forms a liquid-liquid interface between it and water. SOLUTION: A specified amount of water is fed into a granulation tank and warmed to 20-80 deg.C, and a tetrafluoroethylene polymer or copolymer powder obtained by suspension polymerization and having a mean particle diameter of 10 to below 100μm is introduced into the tank. 0.01-5 wt.%, based on the polymer powder, nonionic surfactant and/or an anionic surfactant are added to the mixture under agitation, and 30-90 wt.%, based on the polymer powder, organic liquid which can form a liquid-liquid interface between it and water (e.g. dichloromethane) is added thereto after 2 or 3 min. The entire mixture is heated to 37-39 deg.C and continued to be agitated. After the agitation, the granules are separated from the water and heat-dried to obtain a granular powder having an apparent density of 0.7 g/cm<3> or above, a mean particle diameter of 500μm or below, an angle of repose of 40 deg. or below, a flow rate of 6 or above, a charge quantity of 50 V or below and a surface roughness of a molding of 3.0μm or below. |
