When slabstock is manufactured, stirrers have the task of mixing polyol, isocyanate and additives homogeneously. The mixer is also an important tool for controlling cell structure. Stirrer speed and mixing chamber pressure have a significant influence on cell size. However, the foamer has a dilemma: In conventional stirrer geometries, when pin stirrers are involved chamber pressure changes when the stirrer speed is varied and the pressure rises with increasing size of the cell is changed in two directions: A higher speed allows speed. So the the cell size to shrink and the rising mixing chamber pressure increases it.
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. The new screw-type stirrer provides the foamer with an additional influencing parameter on the size of the cell, opening up new degrees of freedom in cell control.
Other issues of information at Hennecke's INTERZUM booth will be the further developed MULTIFLEX and BFM plants. MULTIFLEX lines are used for the continuous production of various top-quality polyether-based slabstock foams. There are three different plant types and entrants to highpressure technology are offered a standardized plant at an unrivalled value-for-money price. The optional use of the patented NovaFlex®- technology, utilizing the CFC-free blowing agent CO2, permits the manufacture even of foams with densities below ca. 12 kg/m3. For users intending to produce a variety of polyether-based foam types in a discontinuous manner, Hennecke offers the BFM COMPACT slabstock plant. It consists of a single frame, just the day tanks for isocyanate and polyol have to be mounted. Space and assembly requirements are thus minimized.