Posted by
useongroup on Friday, July 03, 2009 2:46:42 AM
Precise feeding of a rubber compound into a
twin-screw compounding
extruder is achieved by using a short single-screw rubber processing
extruder with downstream gear pump.
Hannover, Germany-based KraussMaffei Berstorff has developed an innovative
system for TPE-V production by merging its engineering capabilities in rubber
processing and compounding.
A compounding
extruder with downstream gear pump ensures precise feeding of
the rubber compound into the twin-screw compounding extruder.
The single screw extruder and gear pump combination provides outstanding high
precision feeding performance, said KraussMaffei.
Bale rubber cut into strips can be processed directly instead of having to
use pellets.
Process efficiency and cost-effectiveness are substantially improved since
time-consuming and expensive pre-pelletising of the rubber is no longer
necessary.
The benefits offered by the new KraussMaffei Berstorff system are especially
significant in the production of soft TPE-V types.
In many cases, soft TPE-Vs are produced using oil-extended EPDM rubber, which
is rather difficult to pelletise owing to its sticky surface and because
separating agents must be used.
* Precise rubber feeding - the single-screw extruder ensures reliable feeding
and pre-compounding of the rubber.
A pressure-based control system adjusts the extruder speed in such a way that
the downstream gear pump is always completely filled.
The gear pump is designed to achieve precise volumetric feeding of the rubber
into the twin-screw compounding extruder.
* Compounding process - inside the twin-screw compounding
extruder, the rubber is mixed with the thermoplastics
material, and the cross-linking reaction of the rubber phase takes place to form
the TPE-V required.
The phase morphology and the physical properties of the finished TPE-V are
determined by the configuration of the twin-screw extruder.
The first extruder section is designed for the compounding and mixing of the
main recipe components, usually EPDM and PP, and for the incorporation of
additives and processing oils.
Dynamic cross-linking takes place in the downstream mixing zones of the
extruder.
The last extruder section is used for vacuum degassing.
* Combination with internal mixer - the new system can also be used with an
internal mixer.
In this case, rubber, fillers, plasticiser oils and additives are pre-mixed
in the internal mixer and fed into the extruder in the form of strips.
With this solution, the twin-screw compounding extruder is merely required to
mix in the thermoplastics material and, if necessary, the cross-linking agent
and to perform the dynamic vulcanisation process.
* More about TPE - owing to their superior material properties,
thermoplastics elastomers (TPEs) are becoming increasingly important, said
KraussMaffei.