The present invention relates to a
single screw extruder comprising a barrier screw and a barrel in which the barrier screw is rotatably mounted and which comprises at least a feed zone longitudinal section and a melting zone longitudinal section. The invention further relates to a method for extruding plastic material using such a single screw extruder.
In addition to the aforementioned advantages the
single screw extruder with barrier screw according to the present invention has the advantage that the pressure build-up capability is improved. Compared to the known single screw extruders it is not necessary any more to build up a very high pressure in the so-called feed zone as to enable a predetermined lower pressure at the end of the single screw extruder. With the
single screw extruder according to the present invention it is possible to substantially reduce the pressure between the feed zone and the melting zone. This in turn results in a reduction of wear of the screw in the transition area between the feed zone and the melting zone since it is operated with lower pressures.
This has the advantage that the melting performance of the
single screw extruder may be improved compared with the one channel paired barrier screw. Additionally, the abrasive wear at the primary side bar of the screw may be minimized thereby. The object underlying the present invention is also solved by a method of the aforementioned kind which is characterized in that in the area of the melting zone solid plastic material (solid matter) is transported in a defined quantity out of the solid matter channel into the melt channel. Preferably, the solid matter is transported out of the solid matter channel into the melt channel at predetermined locations along the barrel. Most preferred, the transport of the predetermined quantity of solid matter is caused by the pressure difference between the solid matter channel and the melt channel.
