Internal mixer intermeshing process

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. 

FI CU RE 35.12 Typical fingerprint of a masterbatch mixing process on an intermeshing internal mixer (GK 320E (Harburg Freudenberger) with PES5 rotors styrene-butadiene rubber/carbon black [SBR/CB] tread compound). 

A major problem in cooling rubber, in any process, is its inherently poor conductivity, which means that it is only cooled where it touches a cool surface. Thus, total heat removal depends on the area of the coohng surface and also on the way in which fresh rubber surfaces are moved into contact with that cooling surface. In internal mixers this depends mainly on the geometry of the rotors. Mixers with intermeshing rotors are less influenced by the friction or adhesion between the rubber and metal, and are, therefore, less sensitive to starting temperature. Rotor geometry also affects the overall heat transfer coefficient in a mixer. ... 

With high degradation The rubber bales are milled down together with the filler in an internal mixer with intermeshing blades within a few minutes. Subsequently this mill base is dissolved and compounded with tackifiers and further ingredients in a solution muter. Process time is much shorter, but cross-linking is indispensable even for tapes with standard performance. 

International Polymer Processing 16, No.2, June 2001, p.87-99 NEW-GENERATION CO-FLOW INTERMESHING INTERNAL MIXER... 

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. 

The authors compare the performance of a variable intermeshing clearance mixer, which offers the possibility of varying the intermeshing clearance between the rotors in addition to the usual adjustable process parameters, with that of conventional mixers with intermeshing rotors. 3 refs. Articles from this journal can be requested for translation by subscribers to the Rapra produced International Polymer Science and Technology. Accession no. 773787... 

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