Extrusion Coating Technology for Low Melt Strength Polymers Reduces Edge Bead while Keeping Coat Weight Uniform
Nordson Extrusion Dies Industries Engineers New Die and Deckle Enhancements to Resolve Edge Bead Issues with LLDPE, PP, and High-Performance Co- and Terpolymers
CHIPPEWA FALLS, WI, U.S.A., July 23, 2014: 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—two goals that have often been mutually exclusive with such resins.
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 Extrusion Dies Industries has led to development of a technology package that resolves the issue raised by low melt strength polymers. The trials were carried out at SAM North America’s Extrusion Technology Center in Phoenix, NY. Components of the technology are:
● Dies with lip lands that are substantially shorter than the industry standard. The lip land is the final portion of the flow channel leading to the die exit. In standard dies, a longer lip land plays an important role in maintaining coat weight uniformity, but it also makes possible more of the lateral movement of the melt that generates edge bead. The research by Nordson Extrusion Dies Industries has shown that the gauge profile of the coating can be effectively controlled if the shorter land has been engineered appropriately.
● Suite of secondary internal deckle blades, sized for various polymers. Deckles are used to vary the width of the coating. An internal deckle consists of three independently adjustable components—located at each end of the die—that can be used to fine-tune the edge profile of the polymer as it exits, minimizing bead formation. Tuning is accomplished by varying the positions of the manifold quill and secondary blade with respect to the lip flag and deckle rod (see schematic) In addition to the effects of these differing offset dimensions on the edge profile, the research by Nordson Extrusion Dies Industries has shown that the size of the radius of the secondary blade is another key determinant. While a short radius is effective for LDPE, longer radii do a better job of stabilizing the thickness profile near the edges with polymers having less melt strength.
● Smallest-diameter deckle rod in the industry. The “micro-rod” designed by Nordson Extrusion Dies Industries—half the standard diameter—permits less lateral movement of the melt and thus less edge bead formation.
The short lip land and micro-rod are available in new dies specified by converters focused on making substantial reductions in edge bead, noted Sam G. Iuliano, chief technologist for Nordson Extrusion Dies Industries. The 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,” said Mr. Iuliano. “This development is part of an ongoing research program at Nordson Extrusion Dies Industries to improve productivity and profitability in extrusion coating.”
Photo Captions: 1.) Schematic shows the three independently adjustable edge profiling blades at one end of an internal deckle. The positions of the manifold quill (shown at top) and secondary blade with respect to the lip flag and deckle rod affect the thickness profile of the coating near the edge, as does the corner radius of the secondary blade. Nordson Extrusion Dies Industries can supply a set of secondary blades with differing radii. 2.) Extrusion coating station with an Autoflex® EPC die. 3.) Photo shows a wound roll from a test run in which edge profile control is employed at only one of the ends of the die. There is heavy edge bead buildup at right and barely any that is visible at left. (At both ends the substrate is significantly wider than the coating.)
Nordson Corporation engineers, manufactures and markets differentiated products and systems used for the precision dispensing of adhesives, coatings, sealants, biomaterials, polymers, plastics and other materials , fluid management, test and inspection, UV curing and plasma surface treatment, all supported by application expertise and direct global sales and service. Nordson serves a wide variety of consumer non-durable, durable and technology end markets including packaging, nonwovens, electronics, medical, appliances, energy, transportation, construction, and general product assembly and finishing. Founded in 1954 and headquartered in Westlake, Ohio, the company has operations and support offices in more than 30 countries.
Nordson Polymer Processing Systems provides customers with engineered components to melt, homogenize, dispense, and give shape to plastic and fluid coating materials. Nordson Corporation leverages the collective plastics industry experience from a series of strategic acquisitions to offer a uniquely broad portfolio of industry-leading technologies. Nordson delivers a full range of precision melt stream products — from screws and barrels for extrusion and injection molding — to filtration systems, pumps, and valves — to the extrusion dies and pelletizing systems to meet the constantly evolving needs of the polymer industry.
Nordson Corporation provides customers with local technical sales, service and remanufacturing capabilities through sales organizations and regional manufacturing facilities in over 30 countries.
Sung An Machinery Co. Ltd. (SAM) designs and manufactures an extensive range of machinery and accessories to the printing and converting industry for paper, film, and foil at their worldwide headquarters in Seoul, Korea. Their portfolio of products include extrusion, aqueous, solvent based and solvent-less laminating machines, coating and lacquering machines, rotogravure printing machines and flotation dryers. SAM North America, LLC is based in Phoenix, NY, U.S.A. V.
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