Apparatus for removing moisture and volatiles from molding particulate plastic material feed

Apparatus for removing volatiles from plastic material being fed and plasticized for molding by an elongated plasticizing screw which rotates in a heated barrel, the barrel having a common opening through which the particulate plastic material is received and the volatiles are removed, the screw having a plasticizing portion and a conveying portion, the conveying portion extending upstream from the plasticizing portion to said opening in the barrel, comprising:

• (i) controlled supply means for feeding the particulate plastic material through said opening in the barrel, whereby the rate of feed is controlled to only partially fill the barrel with particulate material adjacent said opening, the controlled supply means comprising uncontrolled feed means connected to supply particulate plastic material to flow control means,
• (ii) suction means connected to apply sufficient suction to remove hot volatiles which are released through said opening in the barrel as the particulate plastic material gradually is melted by the heat and shearing forces as it is compressed by the screw, and
• (iii) particulate plastic material guide means connected between the feed means and the flow control means, the guide means having an upper inlet for receiving the particulate material and a lower outlet leading to the flow control means, the guide means including means for raising the temperature of the particulate plastic material as the particulate plastic material flows between the inlet and the outlet of the guide means, including temperature control means which permits selection of the temperature to which the particulate plastic material is heated, the guide means having an outer body extending between the upper inlet and the lower outlet, and a hollow inner body spaced from the outer body with an upper end connected to the suction means, the outer and inner body having walls with apertures therethrough which permit the flow of air but not the flow of particulate material therethrough, whereby the application of suction by the suction means to the inner body draws hot air through the apertures through the particulate material flowing through the guide means to preheat the particulate material to remove moisture,
• whereby the interruption of flow of the particulate material into said barrel opening by bridging of the particulate material across said barrel opening is avoided.