Intermeshing Counter-Rotating Extruders

A typical screw geometry of a closely intermeshing counter-rotating (CICT) twin screw extruder is shown in Fig. 10.27. 

A cross-section through the intermeshing region (see Eig. 10.28) shows that the openings between the channels of the two screws are quite small. 

Cross-section through the intermeshing region in a CICT extruder 

These openings are considerably smaller than in intermeshing co-rotating extruders see also Figs. 10.3 and 10.4. As a result, CICT extruders can achieve relatively positive conveying characteristics. 

The counter-rotating twin screw extruder has a milling type of intermeshing as shown in Fig. 10.29. 

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Therefore, the conveying characteristics of the CICO extruder are not as positive as those of a closely intermeshing counter-rotating extruder (CICT) see also Figs. 10.27 and 10.28. 

Most of the compounds were extrusion compounded in a conical, partially intermeshing, counter rotating twin screw extruder (Haake Reomix TW-lOO). The extruder speed was set at 50 rpm and the barrel temperature profile was set to produce a melt temperature of 260°C at the die. Samples were injection molded in a 31.8 MT Battenfeld press with a 59 cc shot size. Where noted, samples were compounded in a 60 cc Brabender internal mixer and compression molded. 

The desired self-cleaning function led to the development of the intermeshing twin screw. The counter-rotating screw was discarded, because it tended to get blocked by solids and was a poor mixer attention focused instead on the intermeshing, co-rotating extruder. 

The first patent on the precursor of the TSE dates from 1869. However, the first commercial CORI for handling polymers was marketed 70 years later. Several intermeshing counter-rotating twin screw extruders (ICRR) were developed in the 1920-30 s. After the 2nd World War, the corotating, fully intermeshing TSE (CORI) started... 

Waste ground rubber tire powder was devulcanized and mixed with 30 per hundred rubber (phr) natural rubber to give satisfactory vulcanizate properties. An intermeshing counter-rotating twin-screw extruder with constant root and flight diameters of the screw was designed and installed for waste rubber recycling [31]. 

Figure 6.18 Intermeshing counter-rotating screws in a twin-screw extruder.

Figure 1.20 Leistritz modular intermeshing counter-rotating twin-screw extruders [120-124] (a) Tenner CC machine (b) Thiele counter flight machine.

Intermeshing Counter-rotating (or Counter-rotating Intermeshing) Twin-screw Extruder This extruder is considered to be not effective in large-scale manufacturing. 

Tangential (Non-intermeshing) Counter-rotating Twin-Screw Extruder This extruder is used more for latex coagulation, recovery, devolatilization of polymer solutions, and for reactive extmsion. 

Milling type of intermeshing in counter-rotating extruders... 

CICT is closely intermeshing counter-rotating twin screw extruder (low speed)... 

RTD for an intermeshing counter-rotating twin sere extruder... 

The intermeshing counter-rotating twin screw extruders are normally used when narrow residence times for compounding are required, for example, PVC profile extrusion and color-concentrate preparations [84]. 

The industrial use of twin-screw extruders for this purpose revolves extensively, but not exclusively, around intermeshing co-rotating variants. Closely intermeshing counter-rotating designs are widely used for profile extrusion of UP VC dry-blends since they permit close temperature control and exhibit a high conveying efficiency due to the positive displacement of material where the screws intermesh [150]. 

Thanks to their residence time distributions, co-rotating, closely intermeshing twin-screw extruders have assumed a dominant market position. Other machines, such as single-screw and counter-rotating extruders are used only for special tasks. Fig. 4.7 [35]. 

Figure 7.3 Non-intermeshed counter-rotation twin screw extruder with short UD (Panel Continuous Mixer)...

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