Nordson Extrusion Dies Industries has developed enhancements to extrusion coating dies and internal deckles that make it possible for converters to reduce edge bead with low melt strength polymers while maintaining coat weight uniformity.
While standard internal deckles with edge profile control do a good job of reducing edge bead with the high melt strength resin LDPE, they have been less effective with linear polymers such as LLDPE and PP and with more expensive special function copolymers such as ethylene-vinyl acetate (EVA), ethylene-acrylic acid (EAA), and ethylene-methyl acrylate (EMA). Trimming the larger beaded edges developed with these materials is a costly waste of material, since the combination of substrate and polymer coating cannot be reused.
Research by Nordson EDI has led to development of a technology package that, the company claims, resolves the issue raised by low melt strength polymers. The trials were carried out at SAM North America's Extrusion Technology Centre in Phoenix, New York.
A short lip land and micro-rod are available in new dies specified by converters focused on making substantial reductions in edge bead. A suite of exchangeable secondary deckle blades with varying radii is available from the company on a custom designed basis.
"The new technology for coating with low melt strength polymers enables converters to obtain the cost savings of edge bead reduction without sacrificing coat weight uniformity," concludes Sam G Iuliano, chief technologist for Nordson EDI.
www.nordson.com
