2013 Issue 2—Form meets function for comfort, aesthetics and safety

WeLoc adopts metal detectable food-grade DuPont™ Delrin® acetal resin for new bag closure

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DuPont™ Delrin® medium-viscosity Acetal copolymer in a new range of bag closures developed for the food industry, suitable for the snap-closure action and durability at -50°C, and also its ability to be detected by metal detectors.


Metal or X-ray detection is a primary requirement of the food industry to protect against foreign materials causing cross contamination of food, due to breakage or shattering of parts. In most instances, after filling, jars and other food packaging will pass through detectors, which automatically reject those with any detectable contamination.

With these stringent requirements in mind, Swedish company WeLoc - Weland M. AB has deployed Delrin® acetal resin in a new range of food industry bag closures. The material chosen is one of two new food-compliant Delrin® resins developed specifically for food processing equipment components; material handling equipment, such as conveyor chains and hoppers; food manipulation tools, such as cutters, shovels and scrapers; and forms and molds. As well as its detectability, WeLoc also chose the material for its suitability for “snap-closure” action and its durability at -50°C.


These features, combined with the excellent creep resistance, strength, stiffness, toughness, low wear and low friction, offer WeLoc and other food industry suppliers an advanced material capable of replacing metal components in a huge array of applications.


"We tested other materials for this application but chose Delrin®, as it fulfilled a number of our major requirements—use down to -50°C, fully metal detectable and FDA/EU(GMP) compliant,” said Mr. Arne Henningsson, division manager at WeLoc. “The material also maintains its properties well, is insensitive to moisture and it can be pre-colored in the right shade of blue for the food industry."


The WeLoc closure, originally developed in 1983 for liquid tight sealing, has grown to include more than 50 variants in multiple sizes, for the sealing and reclosing of flexible packages across a great many industries and, in the home, as well. They are sold all over the world, under the names WeLoc, CLIP-it and Klippit.


"We strive to produce and supply high-quality products, putting high demands on our partners for development, testing and documentation,” said Henningsson. “DuPont has been a main supplier of the materials for our products since we started almost 30 years ago and we still view them as an important and beneficial partner today and for the future.”


Looking at the wider food processing industry, Delrin® acetal resin offers many potential savings. In conveyors, for example, potential savings include: cost and maintenance savings based on improved design and functional integration; reduced energy consumption due to lighter components; and longer replacement intervals based on excellent wear and friction properties.


Delrin® acetal resin typically does not require additional lubrication, resulting in silent and durable mechanisms, and offers good, clean aesthetics, leading to a cleaner and friendlier working environment. It is also highly resistant to cleaning agents and offers very good behavior under thermal shock. It also promotes ergonomic improvements, thanks to lighter equipment, and offers quieter systems, due to lower noise emissions compared to metal equivalents.


"DuPont was involved from the very start of the project and supplied very good support," Henningsson concludes. "Together with DuPont we are looking forward to developing new materials for our existing assortment and for future products."


WeLoc has also evolved the design of the bag closure by incorporating other value-added features, including grippers for heavy-duty applications, scoops and spoons for bagged contents (animal feed, coffee, flour, etc.) and indented jaws for holding cables.