A new flat-die system introduced at NPE 2006 in Chicago has the potential to revolutionize the production of cast films and coatings by achieving an order-of-magnitude greater number of layers than conventional coextrusions. The technology, based on a patented "layer multiplier" system developed by Dow Chemical (www.dow.com) and licensed from Dow by Chippewa Falls, WI-based Extrusion Dies Industries LLC (www.extrusiondies.com), yields microlayer structures that are said to improve moisture- and gas-barrier properties for packaging, encapsulate gels, and enable converters to economically use high-cost materials.

In a typical configuration, three or more extruders feed melt streams into an EDI-streamlined feedblock, which produces a uniform multi-layer "sandwich"; this in turn is fed into the layer-multiplier. In this device the layers are multiplied in stages: for example, three layers are multiplied into 12, which are multiplied into 48. The finished microlayer structure is then distributed in an EDI coextrusion manifold to the target product width. "We still do not know the practical upper limit," says EDI president Timothy C. Callahan, "but in my opinion, it's possible to produce 50-micron film with 80 layers."

EDI sees much of the barrier-packaging sector adopting layer-multiplier technology. "Microlayer coextrusion promises to speed the incorporation of nanocomposites in food packaging for enhanced barrier, thermal, and mechanical properties," Callahan says.

Dow's patent history for its layer-multiplier technology goes back several years, Callahan points out, and the technology is being used successfully by 3M Corp. for optical films in electronic displays. Excluding such reflective films, the license granted to EDI applies to cast film, oriented film, sheet, and extrusion coating, primarily focused on the packaging sector.