Abstract: A multi-layer extrusion die comprising an integrate consisting of widening plates; each widening plate having respective flow passage for resin, the flow passage having inlet portion and downstream portion, the downstream portion being widened in the transverse direction and flat, a die body holding the integrate, and having a flat flow passage which combines outlets of the downstream portions, and a converter mounted on the inlet portion side of the integrate. The structure of the die is simplified and the cost becomes cheap.

Abstract: Polyester-polysiloxane block copolymers for dental uses are disclosed as low modulus thermoplastic elastomers. The copolymers comprise polycaprolactone residues and poly(dimethylsiloxane) .alpha.,.omega.-diol residues which are linked by ether bonds. The compounds exhibit the property of plasticity by heating and the property of original rubber elasticity by cooling again to room temperature.

Abstract: A method of molding hollow bodies by continuously downwardly extruding a melt of synthetic resin from a die to form a tubular parison, closing and sealing the free end of the parison, holding the parison, cutting the parison thereby forming a cut-off tube with a closed sealed end and blowing a fluid into the cut-off tube retained in the mold thereby forming a hollow body. Certain apparatus modifications are disclosed such that the step of closing and sealing comprises moving sealing members from outside the parison towards its center, bringing the sealing members into contact with each other while filling the resin of the free end into a space provided between the end of a mandrel extension and the sealing members. The holding step consists of holding a portion of the moving parison which becomes the cut-off tube by its outside surface.

Abstract: A die comprising a central core and at least two thickness adjusting rings surrounding the core concentrically therewith and providing a resin passage between the core and the inner thickness adjusting ring and another resin passage between the inner and outer thickness adjusting rings, each of the rings having a planar seat surface. The rings are joined at their seat surfaces to the core, or alternatively, the inner ring is joined to the core and the outer ring to the inner ring similarly, whereby the rings are rendered radially shiftable for adjustment. Each of the resin passages is provided with resin inlets positioned substantially at the same level as the corresponding planar seat surface.

Abstract: A multi-ring die for extruding tubes composed of a plurality of layers comprises a die portion which is composed of a core and at least two rings disposed one around another and defining die passages therebetween and a column-like portion which is equipped with at least two nozzles mounted fixedly on the outer periphery thereof and is formed with passages communicating with the nozzles for feeding resins plasticized at a plurality of plasticizing mechanism into the die passages; each passage in the column-like portion comprising a guide passage and a branch passage having a plurality of branch bores disposed radially. The die of the invention is compact in size and is available even in the apparatus which is adopted for formation of tubes of a single layer. Besides the tube extruded from the die of the invention is even and uniform in thickness.

Abstract: A screw extruder for molding plastics material having an extruding means mounted on a column standing on a pedestal: the extruding means consisting of a prime mover; an extruding unit, separated from the prime mover, having a screw unit equipped with a screw and a speed reduction unit composed of a planetary gear which transmits power to the screw unit, the reduction unit having an input shaft and output shaft aligned with the screw in turn, the output shaft being formed with a piercing hole extending therethrough, and the input shaft being formed with a piercing hole extending therethrough and communicating with the hole of the output shaft; and a transmission assembly for transmitting power from the prime mover to the reduction unit. The extruder is stable free from troubles such as turning over during the operation and transportation thereof and is easy to remove the screw from the screw unit in order to clean the inside thereof.

Abstract: A screw extruder having a screw including a plug formed with flutes by which the flow of material existing in the cross section of a screw channel is divided into a plurality of striations. The order of arrangement of inlets of the flutes is different from the order of arrangement of outlets communicating with the inlets with respect to the circumferential direction of the plug, whereby the flow is divided into rearranged striations.