High pressure processing of PU foam seals and gaskets

As a result, the single-sequence process to injection mould a part and immediately add a PU seal is now available worldwide. KraussMaffei contributes the machinery and the multiprocess solution (injection moulding plus a reaction process). Rampf supplies the polyurethane casting resin engineered for this specific application. The outcome is a continuous production process: the still-hot injection moulded parts are immediately foamed in a high-pressure process. The logistics effort is reduced, because parts need not be stored or even buffered between moulding and foam application.

Rampf's first two-component PU system for KraussMaffei is Raku-PUR 35-3500 HD. It is suited for sealing door modules, automotive fuse boxes or switch cabinets. Parts are tack-free within 1 - 5 min - depending on the system. The seal has a density of 200 g/l and low water absorptive capacity. The foam forms a defined skin and has good mechanical strength. The PU system is available in various grades from liquid to highly thixotropic.

KraussMaffei has further developed its RimStar Nano PU metering machine and its MK 3.5/5UL mixing head for high-pressure metering of very small output volumes as low as 3 g/s. The self-cleaning mixing head is designed to guarantee good mixing of the components and a steady, residue-free pour of the PU systems at low output rates.