The latest advance in co-extrusion technology from Nordson Corp. (Westlake, OH) enables film processors to achieve tighter thickness tolerances for the individual layers in a multi-layer structure. Nordson has manufactured what it claims to be the world's first nine-manifold extrusion die yielding multi-layer film with two-thirds less layer thickness variation. The new technology is particularly suited to processors with high-throughput lines dedicated to a narrow range of products.
A Nordson EDI nine-manifold flat die, the first of its kind, has been successfully commissioned, and is producing nine-layer film from various resins. While the degree of improvement will vary with the application, in general, Nordson EDI's nine-manifold die technology promises to reduce variation in individual layer thickness from the +/-15% tolerance often encountered with comparable advanced feedblock systems to +/-5%, according to Sam G. Iuliano, Chief Technologist for Nordson EDI.
"This greater accuracy achievable with multi-manifold dies enables processors to run thinner layers of the costly specialty materials often required for high-performance packaging films, while at the same time enhancing product quality and consistency," said Iuliano.
"Nordson EDI customers around the world have long benefitted from multi-manifold co-extrusion, using dies with two, three, four or five manifolds," explained Iuliano. "Engineering a nine-manifold die was a big challenge for us, since 10 major die body segments had to be adequately fastened and heated. In addition, the nine flow channels were each custom designed for the specific layer that they were distributing, meaning that we had to accommodate flow channels of varying sizes and layouts in the design."
The company said that having built more multi-manifold dies than any other manufacturer, Nordson EDI has applied its experience to make them trouble-free, noting that many "Nordson EDI four- and five-manifold dies are in operation without leakage issues, even at throughput rates approaching 5,000 kg/h. For the new nine-manifold die, Nordson EDI designed additional fasteners outboard of the main die bodies (in the end plate assembly area) to ensure proper sealing.
The nine-manifold die is the latest in a range of co-extrusion options available from Nordson EDI. The die systems that Nordson EDI recommends for a given application depends on such variables as overall throughput rate, layer thickness and viscosity rations, die width, number and type of product structures needed and whether the melt processing temperatures for any of the melt streams are distinctly different. While the recommended solutions could range from a single-manifold die with feedblock to a full multi-manifold die with separate channels for all layers, often the recommendation falls between these extremes, combining multi-manifold and feedblock approaches.
Even as it develops advances in multi-manifold dies, Nordson EDI is committed to innovation in feedblock design, noted Iuliano. "Depending on the particular processing scenario, a single manifold die with a co-extrusion feedblock may be the best way forward—for example, in a case where the extrusion tooling needs to produce many different structures with vastly different layer ratios. The feedblock approach generally allows for more product versatility as well as simpler cleaning and product changeover procedures," Iuliano added. "The multi-manifold approach is superior, however, in terms of product quality and consistency. Today, this approach is more than ever a practical, realistic alternative for producers of higher-order multi-layer film."