SOLID STATE SHEARING EXTRUSION PULVERIZING

摘要

PURPOSE: To pulverize natural and synthetic polymers by reduced energy consumption without bringing them to extremely low temp. by rotating reversely rotated tapered conical meshing screws at a specific rotational speed to apply normal/shearing stress necessary for forming a fine powder of polymers. CONSTITUTION: A pulverizer has a hollow tapered barrel 13 including a tapered twin-screw extruder having tapered conical meshing screws 14 at least in its powder forming zone. A raw material is supplied to a first zone and softened in a second zone without being melted to be heated to extrusion moldable temp. The raw material is cooled to below its softening point, that is, to 20-100 deg.C in a third zone. A device for applying normal/shearing stress so as to apply force sufficient to perform pulverization is arranged in the third zone. A fine powder is fluidized by air streams to be prevented from flocculation in the rear stage of the third zone and a fourth zone. The diameter of the barrel 13 is increased in the fourth zone and the distance between screw threads of the screws 14 is made large to prevent the flocculation of a powder.