Counter-Rotating Closely Intermeshing Twin-Screw Extruder

Counter-Rotating Closely Intermeshing Twin-Screw Extruder 

The derivation of the flight leakage is similar to that for the flight leakage in a 

The equation for the calender leakage follows the classical derivation for the throughput of a two-roll calender, with the only diflerence being that the velocities of the two calender surfaces are different because of the different 

From the equations above it can simply be deduced that every leakage flow has two components one drag component, proportional to the rotational speed, and one pressure component, proportional to the pressure difference between two consecutive chambers and inversely proportional to the viscosity. The proportionality factors are only dependent on geometrical parameters. The only exception is the tetrahedron gap, which only depends on pressure differences. The total amount of leakage can now be written as  

The volume of a C-shaped chamber can also easily be determined by straightforward calculations. For this we subtract the volume of the screw over the length of one pitch from the free volmne of the barrel over the same length. The volume 

---

K. J. Gadzenveld and L. P. B. M. Janssen, Scale-up of Counter-rotating Closely Intermeshing Twin Screw Extruders without and with Reactions, Polym. Eng. Sci., 30, 1529-1536 (1990). 

In this case study, a urethane prepolymer based on polyalkylene etherglycol and an aliphatic diisocyanate group (methylene-bis, 4-cyclohexyl isocyanate), Adiprene LW-520, reacted with 1,4-butane diol in a counter-rotating closely intermeshing twin screw extruder with dibutyltin dilaurate as a catalyst (5). 

Figure 6.8 Leakage gaps in a counter-rotating, closely intermeshing twin-screw extruder (from [4]).

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]. 

The industrial use of twin-screw extruders for this purpose revolves extensively, but not exclusively, around intermeshing co-rotating variants. Closely in-termeshing counter-rotating designs are widely used for profile extrusion of UPVC 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]. 

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

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

Counterrotating intermeshing twin-screw extmd-ers have the narrowest residence time distribution followed closely by co rotating intermeshing twin-screw extmders. Counter rotating nonintermeshing twin-screw extruders have the broadest residence time distribution. 

A COMPOSITE MODEL FOR SOLID CONVEYING, MELTING, PRESSURE, TEMPERATURES AND FILL FACTOR IN A METERED FED CLOSELY INTERMESHING COUNTER-ROTATING TWIN SCREW EXTRUDER.491... 

---