Process for the production of beads or bead-like granules from molten or heat plastified thermo-plastic polymeric material and apparatus therefor

摘要

880,055. Pelletting plastic materials. DOW CHEMICAL CO. Jan. 12, 1960 [Jan. 15, 1959(2)], No. 1031/60. Class 87(2). A process of making pellets from plastic material comprises extruding the heat plastified material into a confined space which is open on opposite sides and ejecting the material from the space, with simultaneous coding, by introducing a compressed inert material into the space. Details of various solid and cellular composition are given and the compressed inert material may be gaseous or liquid, e.g. water, steam, nitrogen, propane or methyl alcohol. In Fig. 1 a screw extrudes plastic material through peripheral slots 27 in a screw extension 13 that is forced by the pressure of the material against a die member 14. The bearing face of the extension 13 has an annular groove 31 and radial grooves 30. The die member 14 has stepped outlets 24 and an inlet 23, for the inert material, which connects with the grooves 31, 30. As the screw and extension 13 rotate the material passes through the slots 27 in to the outlets 24 until the slots 27 and outlets 24 are out of register, continued rotation of the extension 13 brings the grooves 30 in register with the outlets 24 so that the inert material passes through the inlet 23, grooves 31 and 30 and ejects the plastic material from the outlets 24. The grooves 27 and outlets 24 may have different circumferential pitches to avoid pulsation of the plastic material and inert material. In Fig. 8, a discharge member 36 with outlets 37 rotates around a stationary die member 34 having longitudinal slots 35 and surface grooves 38 leading to groover 39 in the discharge member 36 and a inert material inlet 40. In operation the material is extruded through the slots 35 into the outlets 37 whose rotation brings them over the grooves 38 so that the inert material from the inlet 40 grooves 39 and 38 may eject and cool the pellets. The die has a cleaning outlet 43 uncovered by a plug 42 and the discharge member is rotated by a sprocket 52. The outlets 24, 37 may be of any cross-sectional shape. U.S.A. Specification 2,453,088 is referred to.