Twin rotor machines continuous mixers

The continuous mixer (CM) is a counterrotating, nonintermeshing twin-rotor machine. The Farrel Continuous Mixer (FCM) was the first CM developed (1964) by Ahlefeld et al. (8). It has rotor designs along the principles of the Banbury3 high-intensity batch mixer. 

Originally developed for natural rubbers, foodstuffs, and elastomers, at present these machines are used as a stirred tank reactor or a twin-rotor continuous mixer. Their bearings are exposed mainly to radial, not axial, forces. By using one screw longer than the other, one can separate the mixing and pumping functions. 

What about the machinery The proliferation of different rotors made available for batch mixers over the last few years leads one to believe that this part of the industry is in its infancy, rather than approaching old age. It is likely that further designs will appear, but some specialisation may creep in where particular rotor designs are matched to particular parts of the industry. In continuous mixing machinery, the corotating twin-screw machine appears, at last, to be achieving inroads into the rubber industry, and this is likely to continue. Other continuous compounding machines which have had a measure of success in the past are likely to be reintroduced in modified form, particularly those, like the MVX, which were shown capable of outputs in terms of tonnes per hour. 

Plastication by kneading is done in variable shear roll mixers, in rotor mixers of the Banbury or Wemer-Pfleiderer type, or in twin-screw extruders or in special mixers. Plastication made in two-roll mixers is not economical and it is used mainly for batch production or to mix substances of different natures. For continuous line production, single or twin-screw extruders or a Buss KO-Kneader are used. These mixers or extruders operate in a friction mode this friction is obtained by a horizontal backward and forward motion of the screw. The screw may have threads or flights of regular width or of lai ger width and slantly cut in the rotational direction (see Fig. 14.10). Homogenization in these machines is so efficient that even fish-eyes present in PE and suspension polymerized PVC can be disaggregated [8]. 

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