Single-screw extruder

The invention relates to a single screw extruder comprising a barrier screw and a barrel in which the barrier screw is held in a manner that permits to rotate and comprising at least one feed zone longitudinal section and at least one melting zone longitudinal section ( 23 ). The extruder ( 10 ) is characterized in that the barrel ( 11 ), on the inner wall ( 50 ) thereof in the area of the melting zone longitudinal section ( 23 ), has at least one groove ( 52 ) which runs in a longitudinal direction. The invention also relates to a method for extruding plastic material using a single screw extruder ( 10 ) comprising a barrier screw ( 40 ) which is held inside a cylinder ( 11 ) in a manner that permits it to rotate, whereby the extruder ( 10 ) comprises a feed zone ( 21, 22 ) and a melting zone ( 23 ), and the barrier screw ( 40 ) has at least one solid matter channel ( 49 ) and a melting channel ( 48 ). The method is characterized in that solid plastic material (solid matter) is transported in the area of the melting zone ( 23 ) in a defined quantity out of the solid matter channel ( 49 ) and into the melt channel ( 48 ).