A new reactive injection system raises possibilities for
more design freedom with polyurethane composites.
Bayer MaterialScience has invented a versatile technology for the use of fillers in reactive polyurethane (PU) blends. Called the Solid Injection by Air Stream (SIA) method, solids are transported in a gas stream and only injected into the mixing chamber during the blending phase.
In the currently used batch production system, fillers are often added to the polyol component before it is blended with the isocyanate component in the high-pressure mixing head and reacted.
There are two disadvantages to this method. First, the system components must be adequately protected against wear caused by the solid, and second, large or mechanically sensitive filler particles limit the options.
"With the SIA technology, the components - polyol, isocyanate and filler - are added separately and not blended together until in the mixing head. This avoids the disadvantages of the batch method," says Roger Scholz, a polyurethane expert at Bayer MaterialScience. The plant technology was developed in close cooperation with Hennecke GmbH.
The method enables the use of very light or heavy fillers, or also the combination of different types. Even reactive substances or particles with porous surfaces can be used. This significantly reduces the probability of changes to the fillers and the wear of plant components due to abrasive or corrosive additives. The technology also makes it possible to vary the filler content within a layer or between different layers, such as in a sandwich composite, for example. Bayer MaterialScience operates a pilot plant employing the method in Leverkusen, Germany.
One possible area of application is adding flame retardants to polyurethane parts, regardless of whether they are hard or soft, or solid or foam.