Hennecke remains true to itself
Innovations in slabstock production
For over six decades, Hennecke GmbH has developed and produced high-quality polyurethane processing technology. It is considered the market leader in the field of slabstock plants. But instead of resting on its laurels, the company continues to put more innovations on the market – such as a new screw-type stirrer and a flexible laydown system.
New stirrers for continuous slabstock plants MULTIFLEX, QFM and UBT
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 for example, the mixing chamber pressure changes when the stirrer speed is varied and the pressure rises with increasing speed. So the size of the cell is changed in two directions: A higher speed allows 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.
Flexible laydown system for ester and special foams
Ester foamers generally face the task of dispensing a uniform mixture with a good age distribution onto the conveyor. In practice, the mixer is operated in a traversing way or several different outlet systems are developed and used. Hennecke has simulated laydown flows mathematically in order to develop a new, flexible laydown system.
An interview with Karsten Brückner, Sales Manager Slabstock Plants
What function does the adjustable laydown system fulfil?
Because of the special and flexible outlet geometry it is possible to distribute centrally-pouring reaction mixture with a very good age distribution onto foaming widths of up to two metres at least. This is achieved because an adjustable gap between the upper and lower plates subjects the parts of mixture which flow forward to a significantly higher flow resistance than the amounts of mixture which flow to the side. And because this relationship can be adapted by the gap adjustment, the necessary flexibility for different formulations is achieved. On top of this, the modular design with its easily exchangeable upper and lower plates allows for even more flexibility regarding the different process parameters.
What benefits do the customers have?
The adjustable laydown system means that an excellent age distribution can be achieved in continuous slabstock. Highly viscous mixtures in particular can very well be poured centrally and without traversing, and then distributed onto foaming widths of up to two metres (and more if necessary). This means that a relatively good shoulder structure with a striation-free cell structure can be achieved without a calibration device, which is especially advantageous for ester foams that are often produced without a top paper. Moreover, transitions can be kept short when colours and formulations are changed.
What is the most important area of application?
The most important field of use for the flexible laydown system will initially be the flexible foam area for ester applications. Foamers often work with several different self-made outlets. When it comes to foaming widths of over 1.7 metres, pouring often takes place in a traversing way which almost always leads to striation because reaction mixtures of different age flow into one another.
Have tests already been conducted under production conditions?
Yes, field tests have shown that the foaming widths reached so far can be extended. And in future it will be possible to use a stationary mixer for many foams that have been produced in a traversing manner up to now. Thanks to the high flexibility of the system, only one laydown device will be required to cover a wide range of very different formulations. And by adjusting the distribution unit, formulations can be changed more easily during a production run.
Who can use the adjustable laydown system?
Operators of a Hennecke Ester UBT or QFM slabstock plant can attach the laydown system to their mixer.
Mr. Brückner, thank you for the interesting conversation.
Please contact Dept. Service Retrofit, Mr. Peter Böhm peter.boehm@hennecke.com, Tel. +49 2241 339-210 with your enquiries about the screw-type stirrer or ester laydown system.
