| 摘要 |
1,226,422. Extruder vinyl polymers. PRODUITS CHIMIQUES PECHINEY - SAINT GOBAIN. 21 May, 1968 [26 May, 1967], No. 24200/68. Heading B5A. [Also in Division C3] Foamed unplasticized vinyl chloride polymers are prepared by melting rapidly a vinyl chloride homopolymer or copolymer composition to which an expansion agent has been added and extruding the mixture in a rotaryplate extruder so as to obtain a low viscosity homogeneous mass in which the expansion agent is uniformly distributed and in which, therefore, the gases subsequently released by the expansion agents are also uniformly distributed, the extrusion and foaming operations being carried out as rapidly as possible, after which the foamed products are subjected to thermal treatment to make them rigid. The rotaryplate extruder may comprise a stator and a rotor, the stator containing a circular cavity offset from the axis of the rotor, the periphery of which virtually delimits the gelling and shearing zone of the material that is to be extruded and communicates with a feed hopper, while its central part opens into an extrusion die, the rotor and stator each having at least one set of deflector fins, in the form of an arc or spiral, disposed within contiguous and coaxial annular spaces in the circular cavity. |
