CAPS AND CLOSURES | INNOVATION
Redesigning the closure for circularity
Injection moulders of caps and closures are now required to find solutions for a much wider range of problems, including the use of tethered caps and post-consumer recyclate. Mark Holmes finds more
Caps and closures have always required excellent functionality and shelf appeal for brand owners. However, sustainability and the needs of the plastics circular economy are providing new challenges for injection moulders, resin suppliers and manufactur- ers of injection moulding machines. As well as continued lightweighting, these now include more easily recyclable materials, increased use of post- consumer recyclate and tethered closures. There are a number of significant market trends
emerging at present for the injection moulding of caps and closures, reports Husky. “Firstly, there is health and safety,” says Michael White, Business Manager for Closures. “By default, the existing neck and closure design needs to ensure a hygienic drinking experience from first opening until the package is deposited in the recycling collection box. In addition, there are increased lightweighting and legislative efforts that are designed to improve the sustainability of existing finishes and caps, for example, tethered closure legislation that requires the closure to remain on the bottle. Creating a premium product is also
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a factor, for example, tall and larger neck finish variants that provide a more pleasant opening experience. For commodity-type applications (for example, large case formats), the industry requires ultra-lightweight finishes to maximise production cost savings.” The need for tethering has led to a fundamental
redesign of the closure. “The challenges are numerous,” says White. “For example, a functional hinge needs to be incorporated that is robust and can achieve more than 30 openings and re-clos- ings. In addition, the hinge must be intuitive to operate and have positive shell opening, locking and re-closing functions. It also needs to feature audible and tactile cues to signal when the shell is in the locked position. Additionally, the closure still needs to perform all of its typical functions of sealing, tampering evidence and carbonation retention. Weight neutrality is another design constraint while featuring a tether system that must be able to withstand greater than 25N pull force.” Husky has developed a range
of solutions that address this teth- April 2020 | INJECTION WORLD 27
Left: Husky has designed a re-closure feature for caps
IMAGE: SHUTTERSTOCK
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