Method of processing solid polymer particles of a polycondensate by means of a multi-rotation system

Abstract

A method of processing solid polymer particles of a polycondensate by means of a multi-rotation system (100) comprises: a) intake and partial melting of the polymer particles in a first extruder section (1) having an extruder screw (101) that rotates within a housing recess (51) of a housing (50); b) passing of the partly molten polymer mass containing between 5% by volume and 50% by volume of unmolten polymer particles into a second extruder section (2) in the form of a multi-screw extruder section (2) with a poly-rotation unit (20) and multiple satellite screws (26) that rotate therein, wherein the diameter of the poly-rotation unit (20) is increased compared to the screw diameter of the first extruder section (1) and wherein a transition cone (21) is formed between the extruder sections (1, 2) and a conical gap (52) is formed with respect to the housing (50); c) ambient pressure plastification of the remaining polymer particles by means of passage through a drive zone (23, 24) which is present beyond the transition cone (21) in flow direction and has exposed drive pinions (23) of the satellite screws (26); d) guiding of the polymer mass completely molten in the drive zone (23, 24, 25) onward through a venting zone under reduced pressure; e) removal of volatile constituents from the polymer melt in the venting zone; and f) transfer of the polymer melt to a discharge extruder section (3).

Description

technical field [0001] The invention relates to a method for processing solid plastic particles from polycondensates by means of a multi-rotation system. Background technique [0002] A fundamental problem when handling polycondensates (especially hydrolyzable plastics such as PET) during extrusion is that a certain residence time and a certain heat input per unit time are required to obtain a homogeneous plastic melt that can be further processed, But on the other hand, it is this heat input during the residence time that leads to hydrolytic degradation of the plastic if it contains moisture. However, especially in recycling processes, it is not economical to completely dry the solid matter before feeding it into the extrusion process, so PET recycled material must always be considered wet. As a result, solid plastic with residual moisture is sucked into the extruder, melted and degassed to remove condensed water, thereby stopping hydrolytic degradation and even starting a...

AI Technical Summary

Problems solved by technology

The only known way out of the above-mentioned dilemma is a more intensive in-line pre-drying of the sucked-in solids before feeding them into the extruder, with correspondingly disadvantageous consumption of time and costs

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