Under the spotlight

Reduce, reuse, recycle’ may have been coined in the 1970’s, but it is coming of age now as the environmental agenda drives consumer and producer changes throughout the food industry. From the rising cost of recycled plastics creating challenges across the board, to major brands such as Coca-Cola shifting to tethered caps on disposable PET bottles of their iconic soft drinks, every area of packaging is being reassessed.

As retailers and producers alike make changes to try and improve their sustainability credentials, even the humble induction heat seal is being reviewed. Here Darren Dodd discusses how environmental pressures are increasing demand for simpler, mono-materials in liners and the challenges this presents.

The mismanagement of waste is a global issue that companies and governments across the world are trying to resolve. Recent Eurostat data shows that the second most common type of packaging waste in Europe is plastic packaging and the amount produced per kilogram per person has slowly but steadily risen from 2009 to 20191. As governments impose a range of policies intended to curb this trend, even liners are being placed under the spotlight. The difficulty however is, how to replace these small yet mighty liners with replacements that deliver in terms of performance as well as recyclability?

The secret of induction heat seal success
Induction heat sealing’s success lies in its use of a laminated structure – or liner – to apply a hermetic seal over the mouth of a container. Once the cap is applied to a container, aluminum foil within the liner is heated by induction heat sealing, causing a layer of heat seal material to bond securely to the rim (also known as the land area) of the container, creating a strong airtight seal.

This packaging solution has evolved to create hermetic, leak-proof seals that can be tailored to be tamper-evident, branded and easy-to-open if needed. Also, as a result of increasing ecommerce, many producers have shifted to induction heat seals over the past two years to overcome increasing leakage issues. In fact, many international shipping companies now require the use of induction liners on liquid products to protect their distribution channels.

Multiple to mono?
Despite induction heat sealing being able to meet the challenges presented by many wide and varied distribution networks, many induction heat seal liners used on bottles and jars are made from multiple materials. Liners can be recycled using chemical recycling, however they need to be cleanly removed, so that the containers they are attached to can be fed into the recycling stream. With this in mind, it is not surprising that there is growing demand for common materials in the whole pack to ensure the liner and container can be recycled as a whole. To do this, the humble liner needs to be re-envisioned.

The challenge is now on to develop liners that are simpler, more recyclable and contain more recycled content, whilst also continuing to protect consumers from spoilage and leakage. At Selig, a two-stage process is underway that is exploring what the future of liners looks like. As a result, the environmental agenda has trebled the number of liner developments in process within Selig’s R&D department.

The first stage of focus is on resolving container/cap recycling stream contamination issues. This involves matching liners with the products they are being supplied in, so that no residual foreign material is left on the container or cap. Taking coffee as an example, traditionally a plastic cap with a board back liner was used, with an aluminum and board liner also sealing the container. More and more producers are now replacing the board backed cap liner with a foam backed liner that matches the cap, so it doesn’t contaminate the recycling stream. Also, the way that the liner seal separates from the container is being adjusted to ensure that clean removal is possible, making the container easier to recycle or use in a loop system, without contamination, as well as the cap.

The second stage of focus is that of driving development of liners that promote total recyclability of the product they seal. At present on the market, the mono-material liners available are primarily foam-based. However, as more companies move to using mono-materials and away from two-piece liners, to ensure the recyclability of the pack, the recycling concept will also need to be taken a step further: mono-materials will be used that match the bottle, creating a ‘mono-material whole product’ – so, a PE liner on a PE bottle and a PET liner on a PET bottle.

However, developing ‘mono-material whole products’ that include a liner, aren’t as straightforward as they sound, particularly because laminated liners offer specific sealing benefits that end users have come to expect. Also, foam PE and mono material polyester for example, require sealing in a different way to the aluminum used in induction heat processes. Induction heat sealing has proved so popular over the years just because it is a high-speed, low-cost way of ensuring pack protection and shelf-life extension for producers. Therefore, in the future, a balance will have to be struck between switching to slower sealing production practices and delivering fully recyclable packing, all whilst still ensuring consumer protection.

As can be seen with the challenges facing liner development, it looks like retailers, producers and packaging manufacturers will still have to navigate many challenges when it comes to deciding where the boundary lines lie for packaging recycling and functionality.

1 https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Packaging_waste_statistics

Darren Dodd is Service and Marketing Director at Selig, a leading worldwide manufacturer of tamper evident cap and closure lining materials for use across a broad range of applications, such as food and beverage, pharmaceutical, agrochemical, cosmetics and healthcare. Selig’s comprehensive range of both one- and two-piece structures means that they can manage even the most challenging applications with one of its customized aluminum foil/heat seal combination products. In addition, Selig offers a range of easy open products, which offer greatest convenience and product freshness to the consumer as well as product differentiation to the brand owner.
For further information, please visit: www.seligsealing.com