A device and a method for the heat treatment of thermoplastic melts

A device for treating melts of thermoplastic materials, comprising:

• a housing with a melt inlet opening, a melt outlet opening and a withdrawal opening for volatile components of the plastic melt, comprising a first rotatably driven shaft and a second rotatably driven shaft,
• wherein a plurality of mixing elements are arranged on each shaft axially spaced from one another and rotating with the shaft,
• wherein the mixing elements of the first shaft are axially offset from the mixing elements of the second shaft in such a way that the mixing elements of the first shaft face interstices formed between the axially spaced mixing elements of the second shaft and the mixing elements of the second shaft are axially spaced from each other, and the mixing elements of the second shaft are axially offset from the mixing elements of the first shaft in such a way that the mixing elements of the second shaft face interstices formed between the axially spaced mixing elements of the first shaft,
• wherein a distance (A) between the first and second shafts and a greatest radial length (R) of the mixing elements are dimensioned in a way such that the mixing elements engage in the spaces opposite to them,
• wherein the first or/and the second shaft are/is axially displaceable, and
• wherein the displacement is preferably realized in a pulsating manner.