Micro-Layer Cast Film Process Yields Stretch Wrap with Enhanced Properties and Potential to Save on Wrapping Cost
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CHIPPEWA FALLS, WI, February 11, 2008: "Layer-multiplier" technology applied by Extrusion Dies Industries, LLC (EDI) has yielded micro-layer film that stretches up to 45% more than conventional three-layer products, opening the possibility that users of stretch wrap will need fewer pounds of film to unitize a given number of pallet loads, it was announced today by EDI, which will highlight the technology at Chinaplas (Stand W1F51).
Micro-layer film has an order-of-magnitude greater number of layers than a conventional coextruded film but a similar overall thickness. EDI builds tooling for producing such film as a licensee of a patented "layer multiplier" system developed by The Dow Chemical Company.
In tests by EDI comparing 48-layer micro-layer film with conventional three-layer film produced from the same resins, the micro-layer product stretched up to 34% more in the machine direction before failure in the case of an LLDPE/LDPE/LLDPE structure, and 45% more for an all-LLDPE structure (Photo 1 & Photo 2). Like the conventional coextrusion, the micro-layer film had started out as a three-layer structure, but in the innovative tooling built by EDI these were subsequently multiplied into twelve, then into 48 (Photo 3).
"It has been recognized in the stretch film industry that increasing the number of layers-even if all are produced from the same resin-enhances properties like stretchability, tear-resistance, and puncture-resistance," said Mark D. Miller, manager of EDI's New Products Group. "By going from three, six, or nine layers to literally dozens, layer-multiplier technology promises to yield stretch wrap with the potential to save on raw-material costs and at the same time reduce the amount of post-industrial solid waste."
The proliferation of layers in micro-layer film provides another advantage of special value in stretch film, Miller noted. "The greater the number of layers, the less the likelihood of breakage caused by gels, pinholes, and other defects. This is because the large number of layer-to-layer interfaces increases the chances for defects to be encapsulated and rendered harmless."
Other Benefits of Micro-Layer Film Show Great Promise in Food Packaging
By preventing web breaks, the encapsulation of defects in micro-layer structures has advantages in many other applications besides stretch film, according to Miller, and there are benefits of particular importance in food packaging.
"In packaging film produced with barrier resin, the sheer increase in the number of barrier layers creates a 'torturous path' for gas and moisture molecules between ambient air and the food contents inside a package," Miller said. "For this reason EDI expects layer-multiplier technology to achieve widespread use in barrier packaging."
In a typical layer-multiplier production line, three or more extruders feed melt streams into a streamlined feedblock, which produces a uniform multi-layer "sandwich"; this in turn is fed into a layer-multiplier device (Photo 4), which multiplies the layers in stages. The finished micro-layer structure is then distributed in a coextrusion manifold to the target product width.
The key role of EDI is to make the Dow technology commercially accessible and then to license it to extrusion processors and web converters. The tasks carried out for each customer by EDI in its role of system integrator will include: 1) designing feedblocks to present the proper layer structure to the multiplier device, 2) engineering the multiplier device to provide the pressure drops and balanced polymer flow channels for combining materials of differing viscosities and flow rates, and 3) machining streamlined manifolds to distribute the microlayer structure to final width. To carry out this work, EDI has equipped a 5,000 sq.ft. (465 sq.m) process development laboratory to run a wide range of film and sheet structures; the lab is part of the EDI Technology Center, a new 19,600 sq.ft. (1,820 sq.m) research and test-run facility located near the company's world headquarters in Chippewa Falls, WI, U.S.A.
EDI Precision Dies (Shanghai) Co., Ltd., or EDI China, is headquartered at 99 Zhongde Road, Songjiang Science & Technology Park, Songjiang, Shanghai 201614, China. Tel: 86-21-578-50918. Fax: 86-21-578-50698. Email: edishanghai@extrusiondies.com. General manager is Jason Q. Yin.
EDI is represented in China by KODAMA CHEMICAL INDUSTRY CO., LTD., Flat G, 15/F, Yan Dang Building, No. 107, Yandang Road, Shanghai 200020. Tel: 86-21-331-00275. Fax: 86-21-331-00275. Email: kodama@online.sh.cn. Contact: Ryo Amagi.
Extrusion Dies Industries, LLC is a leading international supplier of flat dies for sheet, film, extrusion coating, slot die coating, and pelletizing. The company designs and manufactures dies, feedblocks, deckling systems, vacuum boxes, and related equipment. Its subsidiaries include EDI GmbH in Reichshof-Wehnrath, Germany, and EDI China in Shanghai. In the U.S.A., Germany, and China, EDI operates facilities dedicated to reworking its own dies and those built by other suppliers, and it has licensed a fourth rework facility in Japan. Headquartered in Chippewa Falls, Wisconsin, U.S.A., EDI sells half of its dies outside the United States. Visit www.extrusiondies.com and www.reworkdies.com. E-mail: sales@extrusiondies.com.
