Mixing equipment twin screw

The aliphatic-aromatic poly(ester)s discussed above are prepared from butanediol and a mixture of adipic acid and terephthalic acid. Blending can be performed on twin-screw extruder equipped with a medium shear mixing screw. 

Fig. 10.4 Hexalobal, intermeshing, counterrotating twin-screw mixing screw elements. [Reprinted by permission from W. C. Thiele, Counterrotating Intermeshing Twin Screw Extruders, in Plastics Compounding—Equipment and Processing, D. B. Todd, Ed., Hanser, Munich, 1998.]...

The two apexes, where the two barrel lobes meet, are commonly truncated to promote axial mixing. The truncation ability eliminates some common fabrication and mechanical problems in twin-screw equipment. Finally, tight melt sealing is difficult to achieve, because of the open design features of the tangential TSEs. 

There are systems, which provide a dedicated mixing system. The use of mixing within a co-rotating twin-screw extruder system is described by Kleinebudde et al. (13). This system also claims the ability to be able to adjust the water content to the appropriate level and because it acts as both mixer and extruder, reduces the number of items of equipment required. This system is not widely employed in screen extruder systems, which without careful formulation can generate considerable heat that could be detrimental to heat sensitive formulations. Hellen et al. (14) describe the use of a granulator (Nica M6L, Nica systems AB, Molndat, Sweden) that functions with a high speed turbine to mix the powder with the water prior to extrusion. 

Polyamide-6 (PA-6) and polypropylene (PP) are both semi-crystalline polymers and the combination of an engineering plastic (PA) and the best commodity product (PP) could lead to new blends with Interesting Intermediate properties. We tested systems containing 50 wt% of each product and the ones obtained by addition of 3% of the reactive PP-g-AM resulting from previous continuous grafting in the extruder. The blends were prepared by simple mixing in the ZSK 30 twin-screw extruder and the samples for mechanical testing were molded by injection in a BILLION equipment. 

Dispersion-type screw mixers are in an entirely separate class from the extruder designs described above. They are applicable to processing of either dry materials or moderately viscous pastes, creams, or lotions. These machines normally consist of a conical vessel equipped with a conical or inclined screw. There are either single- or twin-screw models that provide a gentle mixing action, and thus... 

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