Extruder having screw elements with a particularly large pitch in the region of the gas venting opening, and use of said extruder

An extruder having two or more screw shafts rotatable in the same sense and at the same speed, wherein the extruder comprises a housing having an inner housing diameter Di,

• wherein the extruder has at least one vent,
• wherein, in the entry region of the at least one vent,
• each screw shaft has at least one high-pitch screw element having a ratio X of pitch T to
• inner housing diameter Di of 1.75 to 15,
• or
• has at least one asymmetric screw element,
• or
• has at least one screw element mounted eccentrically on the axis of rotation of the screw shaft, wherein the high-pitch screw elements
• or
• the asymmetric screw elements,
• or
• the screw elements mounted eccentrically on the axis of rotation of the screw shaft, are each immediately adjacent and opposite one another on immediately adjacent screw shafts,
• wherein the entry region of the at least one vent is a section of the extruder having a position based on the first edge of the vent in conveying direction, wherein the entry region is configured to:
• (a) begin at a point at 100% of the length of the vent in conveying direction before the first edge of the vent, and
• (b) end in the vent at a point at 50% of the length of the vent in conveying direction,
• and
• from the first edge of the vent in conveying direction of the extruder, the at least one high-pitch screw element in each case,
• or
• the at least one asymmetric screw element in each case,
• or
• the at least one screw element mounted eccentrically on the axis of rotation of the screw shaft in each case,
• extends into the vent for 0% to 50% of the length of the vent,
• and
• the at least one high-pitch screw element in each case,
• or
• the at least one asymmetric screw element in each case,
• or
• the at least one screw element mounted eccentrically on the axis of rotation of the screw shaft in each case,
• commences in a conveying direction before the first edge of the vent in the conveying direction and extends at least to the first edge of the vent in the conveying direction, wherein the at least one high-pitch screw element in each case or the at least one asymmetric screw element in each case or the at least one screw element mounted eccentrically on the axis of rotation of the screw shaft in each case is followed directly in conveying direction by at least one low-pitch screw element in each case having a ratio X of pitch T to inner housing diameter Di of less than 1.5.