Mixing equipment roll-mill

Polyethylene can be compounded on any of the standard types of mixing equipment used for visco-elastic materials. For laboratory purposes a two-roll mill is suitable operating temperatures varying from about 90°C to about 140°C according to the type of polymer. On the industrial scale, compounding is undertaken either in internal mixers, or more particularly, extrusion compounders. 

The application of two roll mills in the downstream of such mixing lines is preferred, especially if the two roll mills are equipped with stock blenders (Figure 35.14). After discharging, the rubber batch will be sheeted on the two roll mill. By putting the sheet through the stock blender, the free surface from which the ethanol and moismre can be evaporated is rather big allowing the chemical reaction to proceed even at somewhat lower temperatures. A smdy by Zuuring et al. has shown... 

While the Dove composition described in Table 9.4-2 was processable at reasonable line speeds on a conventional soap processing line (roll mills, extruders, stampers), some equipment modifications were necessary. For example, whereas soap is normally mixed in large agitated tanks, the Dove mixture had a much greater viscosity and therefore required use of a steam-jacketed kneader mixer such as those used to make bread dough, pastes or mastics. 

Fillers may be added to low-viscosity resins by conventional sigma-blade mixer or the same type of equipment used for mixing paint systems. Three roll mills are generally employed for more viscous systems to obtain thorough wetting of the filler by the resin matrix. 

Hardeners such as dicyandiamide need to be ground using equipment like a three-roll mill (Figure 21.70) to ensure proper distribution. Mixing is important and high shear and static mixers are used. Wet resins dissolved in solvents can be coated by many techniques (Figure 21.71) normally onto a silicone coated release paper, supplied with a differential... 

In the dry procedure, the silane is sprayed onto well-agitated filler. In order to obtain maximum efficiency, uniform silane dispersion is essential through the shear rates provided by the mixing equipment, for example, kneaders, Banbury, Hauschild, Primax, and Plowshare mixers, two-roll mills, or extruders [19b]. Most important commercial silane coating processes are continuous and have high-throughput rates. Silane addition control, dwell time, and exact temperature control within the system are essential. All parameters need adjustment depending on the type of silane employed. 

Mixing. The ability to be mixed in existing equipment used in natnral Rubber Compounding (qv) was one factor that contributed to the easy acceptance of polychloroprene after its discovery (Table 9). Mixing of compounds of varions sizes can be performed on two-roll mills or in an internal Banbury mixer. A typical 20-min procedure follows ... 

---