In close cooperation with its former subsidiary, polyurethane machinery manufacturer Hennecke (St. Augustin / Germany; www.hennecke.com), Bayer MaterialScience (BMS, Leverkusen / Germany; www.bayerbms.com) has developed the Solid Injection by Air Stream (SIA) process for incorporating fillers into reactive polyurethane (PU) blends. Here, the solids are transported in a gas stream and only injected into the mixing chamber during the blending phase. The technology, now being tested in a pilot plant at Leverkusen, will be presented at the upcoming “JEC 2011” composites show, to be held in Paris from 29-31 March.

According to BMS, the new method “opens up entirely new possibilities for the use of composite materials,” whether hard or soft, solid or foam. One envisaged application is adding flame retardants to polyurethane parts. Under the currently used batch method, fillers are often added to the polyol component, blended with the isocyanate component in the high-pressure mixing head and then reacted. The disadvantages of this, the company says, are that the system components must be adequately protected against wear caused by the solid and that large or mechanically sensitive filler particles limit the options.

The SIA technology, in which the polyol, isocyanate and filler are added separately before being blended, is said to enable the use of very light or heavy fillers or the combination of different types, including reactive substances or particles with porous surfaces. Bayer says this “significantly reduces the probability of changes to the fillers and the wear of plant components due to abrasive or corrosive additives.” It adds that 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.