Tangential Rotor Internal Mixers

MACHINE FOR TREATING RUBBER AND OTHER HEAVY PLASTIC MATERIAL. APPLICATION FILED IAN. ID, IDI6. 

Kobe four-wing H rotor Courtesy of Kobe Steel Limited) 

High Distributive Mixing rotor Courtesy ofTechint Pomini) 

Reduction in coefficient of variation, rheometric properties n/a between 30 and 50% 

Reduction in standard deviation, mechanical properties n/a between 20 and 30% 

---

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. 

Technical featiues of the MCC series of tangential rotor internal mixers developed by Comerio Ercole are described. 

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. 

The friction ratio between the rotors of a tangential-type internal mixer as a possible control parameter for the mixing process is studied and discussed. No refs. POMINl... 

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. 

An analysis of the flow behavior which is more or less confirmed by numerical simulations is presented by Leblanc. " The total flow in an internal mixer (tangential type) can be divided into a laminar, circulating flow which is pushed by the rotor tip, an axial directed flow, as an effect of the helix angle between axis and rotor wing and a leakage flow between rotor tip and mixing chamber waU (refer to Figure 35.6), or... 

It is well known that the cycle time of the mixing process in an industrial-sized internal mixer is limited by the increase of the compound temperamre. For example, typical mixing times on a 400 L tangential mixer with four wing rotors is of the order 200 s as can be derived from Figure 35.2. Especially during the last mixing phase the temperature increase of the compound is approximately l°C/s. 

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

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

Friction ratio - The ratio between the differences in rotational speed of two rotors in a tangential internal mixer, or between the rolls of a two-roll mill. 

The feamres and technical benefits of the Hagglunds drive concept for tangential internal mixers are described. The drive concept with power unit and hydraufic motor directly mounted on the machine is illustrated and white area analysis data from three different samples produced in an internal mixer equipped with an adaptive drive concept, called Maximum Rotor Control, and in a internal mixer utilising standard settings with a fixed rotor speed ratio, are presented and discussed. 

The frietion ratio between the rotors of tangential mixers is examined as a parameter for the control of the mixing process. Reference is made to internal mixers developed by Meccaniche Modeme in collaboration with Kobe Steel. MECCANICHE MODERNE SPA KOBE STEEL LTD. POMINI... 

A survey is made of trends in internal mixers for use in the rubber industry, and developments by Krupp Elastomertechnik and some other leading machinery manufacturers are examined. Aspects discussed include the operation of tangential and intermeshing rotors, wear resistant materials for mixer components, the replacement of pneumatic rams with hydraulic rams, optimisation of the mixing process through the use of variable speed drives, and developments in mixing technology for the preparation of silica filled tyre tread compotmds. 20 refs. 

---