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.
Generally
single screw extruder is known. They typically comprise an extruder plastification barrel in which a screw is rotatably mounted. A powdered or granulated initial material (with stabilizers, slip additives, if required thermoplastic materials being added with fillers and colorings) is fed at one end of the barrel and is transported by the rotating screw through the barrel to a so-called demoulding tool or matrix located at the opposite end. At first, the initial material is conveyed or transported through the so-called feed zone and is thereby compressed. This feed zone is followed by a melting zone and plastification zone, respectively, in which the initial material is melted by friction at the barrel inner surface. The melting process mayparticularly when starting the extruderbe supported by an outer heating of the barrel via (mostly electrical) heating elements. Depending on the application the melting zone is followed by a homogenizing zone and a demoulding zone in which the plastified material is prepared for further processing.
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.
