Abstract: In an apparatus for the continuous static mixing of flowable substances in a tubular housing with mixing inserts, the peripheral flow in the housing and the ease of manufacture of the mixing inserts are improved by having the mixing inserts composed of planes provided with intersecting throughflow slots and webs, in which the webs of both planes form a single piece with a transversely extending connecting web and the throughflow slots extend to the housing wall.

Abstract: A mixing insert of solid material into which intersecting channels are drilled is particularly suitable for use as a static mixer for highly viscous liquids. The insert provides a high quality of mixing while withstanding pressure differences of more than 10.sup.7 Pa along the mixer. If the insert is rotated, static and dynamic mixing properties are superimposed on each other in the mixer. Either forward transport of the materials or return for remixing can be particularly promoted according to the sense of rotation and form of the external channels, which must be partly open.