Tangential rotor

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

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. 

FIGURE 35.18 Example of a two-wing (tangential) rotor (2WS rotor of Kobe Steel Ltd). 

Three types of mixer are recognized, plus a miniature mixer which would provide just enough compound for a curemeter test and one sheet. Mixers types A] and A2 and the miniature device have non-interlocking (tangential) rotors whilst type B has interlocking rotors. Dimensions of the larger mixers are specified fairly precisely, including new and worn rotor clearances, and they are required to have temperature control, a system to record power or torque and a timer. The miniature mixer is only specified in terms of capacity, rotor speed and friction ratio but is required to control of temperature, indication of power and a timer. 

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

As a tangential rotor type mixer, a Werner and Pfleiderer GK-2 internal mixer was used with a chamber volume of 3150 cm. The mixer was operated at a fill factor of 76%, the optimum with regard to mixing efficiency for such a type mixer. Rotor speeds of 46 and 50 rpm were used, running at a friction factor of 1.1. A ram pressure of 5 bars (maximum oil pressure on the plunger of the ram) and a wall temperature of 40°C held constant throughout the mixing cycle. 

Engine power 25 (kW) 20 15 10 5 - x Tangential rotors, EPDM-E Tangential rotors, EPDM-D ... 

Fig. 7 Motor power versus mixing time, tangential rotor mixer.

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

The intermeshing rotor type mixer consumes about three times higher specific mixing energy per unit time than the tangential rotor mixer, due to better heat transfer to the mixer walls and subsequently to the cooling medium. 

In time, the carbon black dispersion reached is slightly better for the intermeshing type rotor mixer than for the tangential rotor mixer, irrespective of the molecular mass distribution of the EPDM. 

There are two basic designs of rotor tangential and intermeshing (see Fig. 5). Tangential rotors, like the rolls of a mill, can rotate independently and, therefore, at different speeds. Intermeshing rotors, like gear wheels, if of the same diameter, have to rotate at the same speed. Both types have had their proponents, but until recently there was little factual evidence in the hterature to enable an objective comparison. 

Ellwood showed that in the Banbury mixer, which has tangential rotors, it is necessary to adjust the temperature of the metal in contact with the rubber in order to achieve the necessary degree of adhesion between them. 

Tangential rotor internal mixers - Mixers which are arranged sueh that the predominant mixing aetion is to shear the mixing eompound against the sides of the mixer. 

Tip width - The width of the mixing tip of, particularly, tangential rotors over which the materials must flow. This is normally expressed as a dimension perpendicular to the wing angle. 

The conventional two-wing rotor (Figure 4) has been, and eontinues to be, the most widely used style of tangential rotor. The reason for this is not that rotor developments by major manufacturers have been ineffective, but that the style of rotor is easy... 

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