Sankt Augustin, Germany -- A new stirrer design for continuous slabstock plants from Hennecke GmbH allows users to decouple the speed of mixing from the mixing chamber pressure and hence gives tighter control over cell size.
In making block foam, the stirrer has the task of homogeneously mixing the polyol, isocyanate and additives. The mixer is also an important tool for controlling the cell structure, Hennecke points out.
With conventional pin stirrer geometries, chamber pressure rises when the stirrer speed is varied. But also, higher speed causes cell sizes to shrink while rising mixing chamber pressure increases cell size, Hennecke explains.
Because of its geometry, Hennecke's new screw-type stirrer has a conveying effect on the mixture. Thus the speed is decoupled from the mixing chamber pressure. The screw-type stirrer can especially help reduce the pressure in unfavourable conditions.
Hennecke says its new screw-type stirrer provides foamers with an additional control parameter on cell size.
The stirrer is suitable for Hennecke's continuous slabstock plants: MultiFlex, QFM and UBT.
Hennecke will be displaying this new development, and other foam technologies, on Stand B 037, Hall 9.1 at Interzum 2011, to be held 25-28 May in Cologne.