Agglomerates breaking

Agglomerate breaking device shown in broken line. Spray nozzle shown in dotted line. Tumblers of this type available plain or with either or both of the above features. 

Processes which melt mix polymer and filler are capable of generating the high shear stresses necessary to cause agglomerate break up, together with re-distribution of the primary filler particles. Since its conception in 1835, the two-roll mill has proved to be an effective means of mixing additives into plastics and rubber and is still in widespread use today, principally for laboratory purposes, but to some extent in large-scale industrial applications. 

Figure 10.15. Some mixers and blenders for powders and pastes, (a) Ribbon blender for powders, (b) Flow pattern in a double cone blender rotating on a horizontal axis, (c) Twin shell (Vee-type) agglomerate breaking and liquid injection are shown on the broken line, (d) Twin rotor available with jacket and hollow screws for heat transfer, (e) Batch muller. (f) Twin mullers operated continuously, (g) Double-arm mixer and kneader (Baker-Perkins Inc.), (h) Some types of blades for the double-arm kneader (Baker—Perkins Irtc.).

The broken-line portions of Fig. 19-9 and b show some types of agglomerate-breaking devices for tumblers. 

Measure for the ease with which, under specific conditions (e.g. in liquids), an AGGLOMERATE breaks down into primary PARTICLES. 

The mutual rotation speed of the rolls is, independent of the adjustments of their position, always different. Thus when a semi solid mass with incorporated agglomerates are transferred between the rolls and subsequently are transported from the slower to the faster roU, shearing forces are being exerted on the agglomerates, breaking them up into the primary particles. 

Once incorporation is accomplished, carbon black agglomerates break into aggregates via the onion model mechanism. When agglomerates practically disappear and disintegrate into aggregates, the mixing is considered to be complete. However, every portion of the compound must have the same composition namely distributive mixing is also important and must occur simultaneously with dispersion. 

During the dispersion process, not only the rubber particles but also the carbon black agglomerates break. Therefore, the mechanism of breaking of carbon black must be included in the dynamic model of mixing. However, this aspect is relegated to the future refinement of the model. 

---