| Toyo Seikan’s solution to venting off steam |
| By Stuart Hoggard | |
| 25 July 2006 | |
|
Japan - Vapour pressure build-up has always been a problem with microwavable packaging, but Toyo Seikan has used its weakness to deliver a solution to today’s pressurised urban lifestyle.
Standing at one of the many confusing exits at downtown Tokyo’s Shinjuku station, salary men, and more importantly salary women, rush past with hardly a second glance at the slightly lost foreigner waiting at the wrong exit.
This hectic pace of life is impacting on their spending behaviour and
is a well-known formula governing the packaging supply chain.
We
take a holistic view of package design. It is a combination of pure
science, market knowledge and cost accounting with just an occasional
dash of inspiration.
Rarely is Toyo Seikan content to allow the market to lead it: “We constantly have to challenge the market and ourselves. Why is a pack like that? Can we do this differently? Better? Cheaper?” Taking the vapours Boil-in-the-bag retortable pouches have been around for more than 30 years, and have been eating market share from glass and metal cans for many years; in 2002 Japan’s retortable pouches held 30 per cent market share with more than 280,000 tonnes. A barrier to further growth has been the speed and convenience of the microwave. The main difficulty with microwave cooking has been the rapid build up of scalding steam inside the pack which causes it to expand and explode dangerously. Toyo Seikan’s solution was to develop a high burst strength multi-layer
pouch as a composite of CPP, ONY and PET and use the problematic steam
build-up as a positive property of the pouch.In effect, the boiling steam turns each pouch into a pressure-cooker in a bag, yet with no risk of explosion due to its multi-layer structure, also quirkily named ‘SCOOP’ (which stands for Stress Concentrate Opening). Essentially, this is an automatic vapour release valve built into the pouch. When the liquid contents of a bag are subjected to heat in a microwave, steam is created, which expands in the bag in a uniform manner; the bag itself expands like a balloon. “This creates a stress concentration circle with pressure building up uniformly in all directions simultaneously,” according to Watanabe. “If the steam is allowed to continue its build up, the bag will rupture at the weakest point (the middle of the seam), away from the stronger corners. “What was needed was a valve which would open to release the steam when the pressure reached a critical level. But it also had to remain inexpensive; since it is a single use pouch which gets thrown in the recycling bin after opening there would be no budget for additional expensive valves.
“We achieved this by developing a process which crimps one corner of
the pouch and punches a hole completely through. This deliberately
weakens the barrier to create a reduced stress focal point.” Despite the apparent simplicity of SCOOP, the science goes well beyond what one would normally expect of a container maker’s commercial offering to the brand owner. The high strength properties of the combination of substrate (CPP, Nylon, and PET), creates a high pressure-resistant pouch sealed along all four edges. However, at the weak point - the crimped and flattened corner - the punched hole means that the only actual barrier is the CPP without the nylon and PET reinforcement, which at the critical point of steam build-up minutely ruptures to release the steam. It is an ingenious system that uses the microwave to heat and cook the contents under high pressure. By building in a controlled point of rupture, steam is expelled to prevent pressure build up.
It is an ingenious system that uses the microwave to heat and
cook the contents under high pressure. By building in a controlled
point of rupture, steam is expelled to prevent pressure build
up.
Once the microwave’s timed cooking cycle is over, the pouch can be
removed and cut open with no danger of scalding the user, and with the
pressure removed the bag reverts to its previously limp state which is
safe to open. | |