Capping and lidding: Sealing the deal

Lynda Searby, Packaging News, 04 March 2009

 

Thanks to capless induction sealing, the dairy industry's days of crying over spilt milk are long gone. Now packers, processors and consumers are catching on too, says Lynda Searby.

 

There are few packaging technologies that can truthfully claim to have benefited almost every household in the country, but induction sealing is one of them.

 

Ten years ago, leaky plastic milk bottles were the bane of many consumers’ shopping baskets. Milk dripping from carrier bags into car boots was a frequent grumble. And it wasn’t just consumers who were complaining either. Sealing specialist Enercon estimates that 15 years ago, approximately 56 million litres of milk per year were being lost during production and transportation as a result of cap leakage.

 

Then along came ‘induction’ or ‘hermetic foil’ sealing, putting an end to leaky seals and boosting the milk industry’s profits. So what is induction sealing?

 

After filling, the cap (with a foil seal or ‘wad’ inside) is applied and the container is passed under the induction sealing head. The induction head emits an electromagnetic field which rapidly heats the sealing foil. The heat causes the foil to bond to the container and the wax bond between the foil and backing material to melt. When the consumer removes the cap from the product, there is a perfect seal on the top of the container and the backing material remains in the cap as a liner.

 

By contrast, a conduction sealer uses electricity to heat the metal conduction head. When the head comes into contact with the container topped with aluminium foil, the combination of pressure and heat causes the foil to be hermetically sealed to the container. Milk producers might have been the early adopters of induction sealing, but many other branches of the food, beverage, cosmetics and pharmaceuticals industries have followed their example.

 

Geoff Leng, managing director of Capsolutions, believes one reason induction sealing has become more popular is because it has become easier for users to do accurately.

 

"It used to be a desirable process, but difficult to achieve a good result. Now it’s quite easy to achieve a good result," he says. "That’s due to improvements in the machines and the foils. In the past, fillers had to have very accurate, tightly controlled settings. Now the process has become more tolerant. The control systems and electronics are also much more advanced, which means the machines are more user-friendly, run at higher speeds and can be totally integrated within lines."

 

This is backed up by Peter Tindale, business unit manager of Pillar Technologies Europe, who lists flexibility as the main driver behind recent improvements in induction sealing systems. "It’s about making machines more flexible to minimise changeover time between pack sizes and formats, and smaller and easier to integrate into centrally controlled filling lines."

 

Widening appeal

He says this was a major consideration in the development of the Pillar I-Foiler induction sealing system, which was launched at the Easyfairs Packtech exhibition last month. Designed for wet and humid applications, the digitally controlled I-Foiler is said to allow easier integration into a filling line. It can seal diameters from 10-120mm and coil change is said to be a simple, tool-free operation. A touch screen gives access to basic operator controls as well as help and information screens, fault warnings and diagnosis and set-up of all optional features.

 

Induction sealing is no longer the preserve of large, high volume packers and producers either. "I’d say more and more smaller companies are starting to use induction sealing as a wider audience recognises the benefits of hermetic foil sealing," observes Tindale.

 

This is a trend which has played into the hands of Capsolutions, which, besides selling the Pillar range, sells budget hand-held and semi-automatic hermetic sealers under the Capsealer brand. "They are an economy range and are manufactured in the Far East," explains Leng. "We import them, modify them if necessary, test them and CE mark them. For small start-up companies, these machines offer excellent value for money and in the current climate we can see a lot of people being attracted by smaller machines."

 

While some companies are just coming round to the idea of induction sealing, others are embracing next generation technology – ‘capless’ or ‘direct application’ induction sealing.

 

In traditional induction sealing, the induction foil is inserted into the cap prior to filling and capping, after which the filled, capped container passes under an induction sealing head, explains Tindale. With direct application, the foil is sealed to the filled container, and the closure – if any – is applied afterwards. "This starts to bring induction sealing into more direct competition with traditional conduction foil sealing, with the benefits of lower energy consumption, faster sealing dwell times, although not yet faster production speeds, and lower replacement part costs," he adds.

 

Weight reduction

Besides these advantages over conduction sealing, Relco says capless induction sealing offers a number of benefits over conventional induction sealing – mainly in terms of container cost and weight-reduction opportunities.

 

As the hermetic seal is provided by the foil, the cap can be light-weighted to save money, explains Paul Rollason, sales manager at Relco. "You can also reduce the amount of plastic used in the container neck. That’s because you’re not reliant on the screw thread to give you the induction seal, so you can actually remove the thread from the neck of the bottle and use a snap-on cap." With a single-shot product, such as probiotic drinks, you can remove the cap completely.

 

Rollason reckons that the removal of the thread and use of a foil seal can reduce the amount of plastic by 14% in a one-litre bottle with a 36mm neck diameter. The smaller the container, the smaller the saving, but even for a 300ml bottle, material savings of 9% are possible, he says.

 

Capless induction is also beneficial for products that require post-sealing sterilisation. "If manufacturers put containers through the standard induction process, followed by sterilisation, they often then have to remove the cap to eliminate any excess water that could produce bacteria when the product is on the shelf. Capless induction sealing solves that problem," explains Rollason.

 

Investment bears fruit

Companies that have recently invested in capless induction systems from Relco include Nestlé, for its Munch Bunch Squashums yoghurts, which come in a strawberry-shaped PET container, and Lee Kum Kee Foods in China, for oyster sauce, which is sold in a 300ml PET container. At Lee Kum Kee Foods, the sauce has to undergo post-sealing sterilisation, which made capless induction sealing the obvious choice.

 

This installation posed a number of technical challenges that had to be overcome by Relco: the container has to be carefully handled to avoid spilling the product or distorting the bottle, and the neck supported so sealing pressure is not transferred to the base of the bottle. The seal strength also has to be sufficient to withstand post-sealing processing, plus the machine has to incorporate automatic head height adjustment for different sizes of bottles.

 

Induction sealing technology may have advanced considerably in recent years, but there are still some limitations to its use. "There are still many products which cannot be heat sealed today as there are no induction liners capable of sealing liquid products in glass containers without expensive glass treatments," says Tindale. Once this technical hurdle is overcome, more products will be able to be induction sealed.

 

Masterfil has supplied a single-head capping machine to DDD (Fleet Laboratories), a contract packer of pharmaceuticals and toiletries. The machine handles 18 types and sizes of container and a number of caps including screw cap, pump pack and press-on lids. Containers can be automatically fed or hand fed on to the conveyor.

 

The Mastercap single-head inline indexing capping machine can achieve speeds of up to 60 containers per minute, dependent on product, container and cap type. Masterfil says changeovers between cap styles and sizes are made quick and easy by features like push-button height adjustment of capping heads, colour coded change parts and programmable control systems.

 

Optima Packaging Machinery has launched the CFL1, a new machine for applying functional closures. These are closures containing ingredients which are released into the beverage or cosmetic product when it is opened. This preserves the quality of the ingredients.

 

While the foil seal may seem innocuous and unexciting, if it weren’t for those humble little circles, customers would still be finding leaky milk bottles in their shopping baskets.

 

 

SEALING EQUIPMENT ROUND-UP

• Mecaplastic’s S5000 tray sealer will be unveiled at Anuga FoodTec 2009. The system is an automatic and programmable machine for sealing prefabricated trays with cover film, with or without vacuum and gas reinjection

• The AVSealer from Key Technologies is said to provide consistent sealing temperature to eliminate ‘burn through’ and seals that do not hold. The semi-automatic machine is aimed at small to medium-sized fresh produce packers

• The Sealmaster quality control machine from Capsolutions is a hand-held device for checking that induction sealers are correctly set and functioning. Besides detecting faults with the sealer or process, it stores a history log of production date for QA and product traceability records

• Krones has developed a new generation of aseptic capping machines for PET lines that allows bottle diameters of up to 108mm

• The Saxon Sealer SH 2000 from Fischbein features temperature control technology and enhanced airflow, which aids the heat transfer system that seals thicker bags

• Packaging Automation’s Eco-cut tray sealer, launched last year, claims to reduce the level of film packaging waste created during the operation by up to 33%

• Also new last year was the GT1 from Proseal. Marketed as an enhanced version of the company’s F45 Tray Sealer, the GT1 is said to meet the changing requirements of high-speed food production lines