Abstract: There is provided a screw for use in an extruder comprising a melting section and a metering section and a decompression section therebetween so that the head pressure profile along the longitudinal direction of the extruder is higher than atmospheric pressure and has an inflection point, with the result that a high melting performance is attained and a high extrusion stability is ensured even at a high extrusion rate.

Abstract: A mixing device comprising a plurality of mixing elements, each consisting of at least two passages which are arranged parallel, in a row, and are provided with spiral vanes therein, and through which fluid to be mixed passes, and a collecting and dividing chamber which is common to the passages, in which the fluid to be mixed is collected and then divided in subsequent passage, the elements being arranged in series in such a way that a line extending between the centers of the passages in one element intersects the corresponding line of an adjacent element. The elements of the device are also covered.