A new reactive injection system raises possibilities for
more design freedom with polyurethane composites.
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
"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