The present invention relates to new screw elements for multi-screw extruders with pairs of co-rotating and fully wiping screws.

The purging agent of the invention is for use in purging a resin to be purged which includes an ethylene/vinyl ester copolymer saponification resin, the purging agent being a hydrocarbon-based resin composition that contains a relatively large amount of at least one metal salt selected from the group consisting of alkali metal salts and salts of alkaline earth metals, the shear viscosity ratio as determined with the following equation satisfying a specific range.

Shear viscosity ratio=(X)/(Y)

[In the equation, (X) is shear viscosity (Pa.Math.s) at a temperature of 230 C. and a shear rate of 12.2 sec.sup.1, and (Y) is shear viscosity (Pa.Math.s) at a temperature of 230 C. and a shear rate of 1,824 sec.sup.1.]

A hosing cleaning device for cleaning a housing of a screw machine comprises a support unit displaceable relative to the housing, and at least one housing cleaning unit arranged at the support unit for cleaning an inner wall of the housing, wherein the least one housing cleaning unit can be reversibly inserted into the housing. An associated shaft cleaning device for cleaning at least one treatment element shaft of the screw machine comprises a cleaning chamber, in which the at least one treatment element shaft can be arranged, and at least one shaft unit arranged in the cleaning chamber.

A planetary roller extruder for homogenizing, dispersing, pasteurizing, and purposefully controlling the temperature of biodegradable materials that are prone to altering their properties during processing, in particular the properties that rule out further use after the materials have been processed, such as food, medicinal products or pharmaceutical products, different regions being present in the planetary roller extruder. The planetary roller extruder includes a flow conduit having various transitions from one region to a next region in an interior and components being statically and movably installed. A seal is installed between statically installed components, by which seal gaps or cavities present are configured to be closed. A slide ring seal provides sealing between moving components, which are led from the flow conduit in the interior outward to a surrounding area, so as to avoid steps and/or notches along flow surfaces in a transition region of the moving components.