Extruder comprising a particular arrangement of asymmetrical screw elements on screw shafts

An extruder, the extruder comprising:

• two or more parallel screw shafts that rotate in the same sense and at the same speed, wherein the directly adjacent axes of rotation of which all have the same axis spacing a;
• and
• two or more interpenetrating circular housing bores around the respective axes of rotation, wherein each of the two or more interpenetrating circular housing bores has an identical housing inner diameter dg, and wherein the respective directly adjacent bore centres of which have a spacing which is equal to the axis spacing a, and wherein the respective directly adjacent bore centres of which coincide with the centres of the cross sections of the respective directly adjacent axes of rotation of the screw shafts,
• wherein in each case at least two screw elements with an asymmetrical screw profile are situated directly opposite one another on at least two directly adjacent screw shafts, and wherein the screw elements with an asymmetrical screw profile which are situated directly opposite one another on at least two directly adjacent screw shafts clean one another exactly, and wherein the at least two screw elements with an asymmetrical screw profile which are situated on in each case one screw shaft follow on directly from one another axially,
• wherein the screw profile of the second screw element of the at least two directly successive screw elements with an asymmetrical screw profile on a first screw shaft of the at least two directly adjacent screw shafts is a screw profile which is not congruent with the screw profile of the first of the at least two directly successive screw elements with an asymmetrical screw profile on the first screw shaft of the at least two directly adjacent screw shafts,
• wherein a screw profile is asymmetrical if, for the respective screw profile, there is no mirror axis through any point in the plane of the respective screw profile by means of which a screw profile which is congruent with this screw profile can be produced, and
• wherein two screw profiles are not congruent if a first screw profile and a second screw profile cannot be transformed into one another either by rotation or translation on the plane of the screw profile or by rotation and translation on the plane of the screw profile.