Planetary Extruders

A machine has been described (67) which is said to be suitable for compounding elastomers, and consists of a series of planetary units in which an arrangement of toothed rollers rotate around a central rotating 

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Most plastics e.g. polyolefins and polystyrenes and their derivatives such as ABS (acrylonitrile-butadiene-styrene) and SAN (styrene-acrylonitrile) are supplied by the manufacturers in ready-to-use form with most of the above-mentioned stabilizers or simply need to be additionally stabilized with other additives, e.g. antistatic agents and HALS stabilizers, as required. On the other hand, in the case of other materials (e.g. PVC) it is the end user who adds the additives, pigments or preparations. This is normally done on fluid or high-speed mixers, although in the past gravity mixers or tumble mixers were also used. The mixture is then homogenized on mixing rolls, kneaders, planetary extruders or twin-screw kneaders and further processed. 

Arising from these considerations the planetary roller extruder seems to be particularly suitable for the wet and melt agglomeration of pharmaceutical powder blends. In the following is described a system for continuous wet granulation based on a planetary extruder and the usage thereof. 

Molten polymer is delivered by the planetary extruder to the exit of the extruder by the forwarding, or pumping, action of the turning central shaft, the planetary rollers in cooperation with the outer cylinder wall. The uniformity of the discharge pressure will be dependent on the rotational speed and the design characteristics of the planetary rollers and the helix angle of the planetary gearing. The level of the... 

FIGURE 35.31 The planetary gear extruder (supplied by Battenfeld and Entex). 

This section describes fluid mixing technology and is referred to in other sections in this handbook which discuss the use of fluid mixing equipment in their various operating disciplines. This section does not describe paste and dough mixing, which may require planetary and extruder-type mixers, nor the area of dry solid-solid mixing. 

Barothermal treatments were applied directly to catalyst extrudates. In the course of mechanochemical treatments, extrudates were physically milled, loaded into a planetary mill and extruded again after the treatment. 

In these extruders, six or more evenly spaced planetary screws revolve around the circumference of the central or so-called sun screw. The planetary screws intermesh with the sun screw and the barrel. The planetary barrel section has helical grooves corresponding to the helical flights on the planetary screws. This section is usually a separate barrel with a flange-type connection to the feed barrel section. 

The planetary roller extruders are mostly used for processing heat-sensitive compounds, viz. rigid or plasticized PVC formulations [Collins, 1987 Anders, 1979]. The planetary roller section can also be used as an add-on mixer to SSE to improve the mixing performance [Rust, 1983 Huszman, 1983]. Degassing and addition of fillers or reinforcements into melt has also been carried out. 

Anonymous, Planetary Roller Extruder, Battenfeld Extrusion-technik (1989). 

Plain strain compression test 866 Planetary mixers (also Gear pump) 603, 623 Planetary roller extruders 620, 641, 690... 

Special types (ram extruder, planetary roller extruder, cascade extruder, Weis-senberg extruder). 

The mixing of the components is performed in a batch operation in a kind of planetary mixer, whereas the subsequent operations are all continuous. Batch mixing was chosen in order to have the possibility for adjustments and to assure the correct final mixtures. The mixture is then fed into an extrusion press as illustrated as illustrated in Figure 4. Although the Graveliet mixture does not behave as a plastic (e.g., as clay), no major problems arise in this operation. The extrudability seems to be largely controlled by the apparent humidity of the mixture. 

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