Rotor mixers

The variable intermeshing clearance rotor mixer is designed to allow a variable clearance between the intermeshing rotors of the mixer. 

Many compounding processes are configured with a twin-rotor mixer or twin-screw extruder to perform the compounding followed by a single-screw extruder to pressurize the material for pelletization. A typical process is shown in Fig. 13.8. In... 

The Ko-Kneader developed by List in 1945 for Buss AG in Germany, is a single-rotor mixer-compounder that oscillates axially while it rotates. Moreover, the screw-type rotor has interrupted flights enabling kneading pegs to be fixed in the barrel (12). 

The TSMEE is an experimental device developed to study melting and mixing in twin rotor mixers during the Polymer Mixing Study conducted at the Polymer Processing Institute (95). 

B. David, T. Sapir, A. Nir, and Z. Tadmor, Twin Rotor Mixers and Extruders, The Extended Cartesian Flow Analysis Network Method, Int. Polym. Process., 5, 155 (1990). 

For either reactive or non-reactive blends in an extruder, internal mixer, or a miniature cup-and-rotor mixer, similar morphological features were observed. Initially, during melting, the polymers were stretched into sheets and ribbons, which broke into fibers, then in turn into drops. One reason that may explain the reported differences in morphology is the concentration of the dispersed phase — 5 vol% was used by the first authors, whereas > 20 wt% by the latter. More detailed information of this, as well as on the topic discussed in the following part, will be found in Chapter 9 Compounding Polymer Blends. 

Other types of morphological changes during blending in TSE were also observed [Sundararaj et al., 1992, 1995]. The authors reported that both reactive and non-reactive blends in an extruder, internal mixer, or a miniamre cup-and-rotor mixer, show similar morphological features. Initially, during the melting, the polymers stretch into sheets and ribbons that first broke into fibers then into drops. 

Mixing and processing intensive granulation, static mixers, vortex mixers, rotor mixers... 

Figure 3a. Optical micrographis with various fill factors (R-R screw rotor mixer).

White [23,24] observed the circulatory flow behavior using markers with flow visualization technique in the R-R handed screw and double-flighted rotors mixer (Figure 8). This makes possible measurement of the circulation time as a criteria of mixing. Since the flow visualization experiments have limitations in observing the overall flow motion in the mixer, the following experiment was carried out to determine the distribution of elastomers. 

Fig. 7 Motor power versus mixing time, tangential rotor mixer.

B. Difference Between the Tangential and Intermeshing Rotor Mixers... 

The intermeshing rotor type mixer consumes about three times higher specific mixing energy per unit time than the tangential rotor mixer, due to better heat transfer to the mixer walls and subsequently to the cooling medium. 

In time, the carbon black dispersion reached is slightly better for the intermeshing type rotor mixer than for the tangential rotor mixer, irrespective of the molecular mass distribution of the EPDM. 

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