Intermeshing rotor

Figure 8 Internal mixer rotor designs (a) tangential rotor, (b) intermeshing rotor.

Rotary, positive displacement machines in which two intermeshing rotors, each in helical configuration displace and compress the air available in lubricated and non-lubricated construction the discharge air is normally free from pulsation high rotation speed. 

Silica compounds are generally processed in conventional internal mixers, preferably with intermeshing rotors. These mixers are designed and optimized for carbon black-fiUed compounds in which mixing is based only on physical processes. When a silica-silane reinforcing system is used, additionally a chemical reaction, the sUanization, occurs. One of the main influencing factors of the silanization reaction is the concentration of ethanol in the compound as well as in the mixer [25,26]. As the silanization finally reaches an equilibrium, low concentrations of ethanol in the compound are expected to enhance the reaction rate. 

Basically two rotor types are applied in the internal mixer The tangential rotor type and the intermeshing rotor type. The latter one interferes with the adjacent rotor and turns at the same rotor speed compulsory. In the drop door or through the side plates a thermocouple is mounted to record the temperature of the mbber. 

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

In the case of the intermeshing rotor machine the majority of the mixing action takes place between the rotors with the shearing action being created by the rotor design. Unlike the tangential mixers where the rotors revolve at different speeds, the rotors in intermeshing machines run at the same speed. 

Figure 1-5 Intermeshing Rotors from Internal Mixer...

A priori, this condition is satisfied only with intermeshing rotors. Moreover, with polymer melts, normal stresses in shear flow are very large, even at relatively low shear rate for example, in the range of 10 dyn/cm at Y = 1 sec for polystyrene at 180 C (15) (and probably higher with elastomers). Consequently the N./ o ratio is larger for viscoelastic fluids than for Newtonian fluids and therefore the validity condition for using the lubrication theory at the nip is surely not fulfilled. 

The factory system based on internal mixers, screw extruders, calenders, and vulcanization presses has remained basically unchanged in the past half-century. Internal mixers have had major improvements, e.g., intermeshing rotors proposed by Francis Shaw and Company [C16] and Werner and Pfleiderer [L3], and variable intermeshing clearance rotors [PI] proposed by Pomini-Farrel SpA. Sophisticated computer control systems have been introduced. The early single hot-feed extruders have been replaced by cold-feed extruders with increasingly sophisticated design including pin barrel extruders [G7, H12, H13, M18, W16] as well as complex control systems. 

Passoni [PI] of Pomini has developed an intermeshing rotor design where the rotors may be moved transverse to their axes to control the interrotor clearance. 

FIGURE 4.30 Schematic of internal mixers with tangential or intermeshing rotors. 

In the 1930s, there was a major innovation in the rubber industry with the invention of intermeshing rotor internal mixers. A June 1934 British patent... 

Figure 1.6 Cook s June 14 1934 British patent application drawing for an internal mixer with intermeshing rotor. From Reference [43].

Figure 1.7 Four flighted non-intermeshing rotors (a) Lasch and Frei 1938 design (b) Tyson and Comper 1964 design (c) Sato et al. 1979 design.

There have also been new designs of internal mixer rotors, notably by MiDauer [53] of Werner Pfleiderer (Figure 1.8a) and Johnson et td. [54] of Francis Shaw (Figure 1.8b). Passoni [55] of Pomini has described a completely new design of intermeshing rotor internal mixer in which the rotor inter-axial distances may be... 

Differences in Behavior Between Internal Mixers with Tangential Rotors and Intermeshing Rotors, as Influenced by the Molecular Structure of EPDM... 

The intermeshing rotor type mixer was a Francis Shaw K1 Mark 4 Intermix, with a chamber volume of 5300 cm, operated at a fill factor of 54%, being the optimum for such a type of mixer. Rotor speeds of 50 rpm were used, ram pressure of 3 bars (plunger pressure), and wall temperature of 50°C. The rotor geometries of both mixers are shown in Fig. 1. 

Fig. 8 Motor power versus mixing time, intermeshing rotor mixer.

Intemneshing rotors, EPDM-E Intermeshing rotors, EPDM-D Tangential rotors, EPDM-E - —Tangential rotors, EPDM-D r ... 

---