Lightweighting not only reduces consumption of PET resin, but increases productivity and performance, maximises production cycles and, of course, satisfies consumer demand for sustainable development from manufacturers. A few recent lightweighting concepts have been particularly inspirational to the bottled water industry and have been winning entries in previous Water Innovation awards programmes.
For example, French firm Sidel says that lightweighting is now part of almost every request its designers receive from customers. And it’s a similar story for Italian-based PET Engineering, which estimates that 90% of the projects it’s currently involved in are geared towards designing lighter weight containers.
“Some ‘glamour brands’ give priority to the elegance of the container, but these brands represent the minority of the market,” says PET Engineering president, Moreno Barel.
See our special PET gallery that accompanies this article.
The lightweighting of water bottles started in the mid 90s, at the same time that brand owners started selling water in PET. At this time, ‘best in class’ 1.5-litre water bottles weighed about 40g and 50cl water bottles weighed about 22g. By 2006, the lightest 1.5-litre water bottles weighed 30g, while 50cl bottles had slimmed down to 12.5g, according to Husky.
In the last few years, lightweighting has continued to gather momentum, driven largely by environmental pressures. The latest round of development has seen several bottle designers breaking the 10g barrier.
In 2007, Sidel revealed its NoBottle, which weighs in at 9.9g per 50cl bottle thanks to a technology known as Flex.
“Flex technology is based on flexibility, which offers total shape design freedom even for bottles that are 20% lighter,” says Franck Hancard, product manager of packaging for Sidel. “In addition, Flex features shape memory that allows bottles to spring back to their original shape.”
After premiering an 8.8g 50cl still water bottle at the 2007 K trade fair, in 2008 Krones once more upped the ante with a 50cl PET bottle weighing a mere 6.6g.
The company’s Alexander Schau, bottle design plastics division, explains how it achieved this reduction: “The bottle is divided into different functional sections. In the upper section, a small diameter achieves enhanced grip stability for the user. This grip area has been reinforced with grooves, so that the bottle can be labelled when empty. The lower section of the bottle is significantly larger in diameter. This is where the majority of the product is accommodated. In addition, the bottle is stabilised with nitrogen so that it doesn’t collapse during transport and handling. The interaction of thread, closure, material distribution, design and use of nitrogen was crucial in this breakthrough.”
Krones isn’t alone in this achievement. At last year’s Brau Beviale exhibition, PET Engineering unveiled the Bottle Fly – also a 6.6g 50cl bottle.
In theory, lightweighting involves removing weight from the neck finish area and the body. In practice it’s not quite so simple.
“This lightweighting drive has challenged preform mold and blow-mold designs alike,” says Husky business manager of preform systems, Craig Reynolds. “While material usage has an additional benefit of reducing injection molding cycle times, maintaining bottle rigidity becomes more difficult and requires sophisticated bottle design.”
The challenges encountered when trying to produce an attractive, yet rigid lightweight bottle begin at the preform handling stage and continue throughout filling, labelling, packing and logistics.
“The preform as feed stock for the blow-molder has to fulfil certain requirements,” says Alexander Schau. “The design must be suited to handling in the preform unscrambler, heating module and blowing wheel. When the bottle has been blow-molded, it either enters the air conveyor or is passed directly to the filler. The bottle must be suitably shaped for the air conveyor, plus the air conveyor mustn’t generate too much back pressure that could crush the bottles.
“At the filling stage, a groove in the neck finish and an appropriate straight section below the lowest ring of the neck finish are essential for high-speed fillers that work with neck handling. The lowest ring of the neck finish has to have an appropriate design and thickness to be able to take the momentum and head pressure required for capping.”
If the bottle is labelled after filling, he says challenges are introduced by water on the outside of the bottle. In the case of empty bottle labelling, the bottle has to withstand a certain amount of empty top load until it’s pressurised with compressed air for stabilisation.
Advancements in bottle design and production machinery have had their role to play in overcoming these challenges. For example, Sidel attributes its lightweighting success to a combination of factors.
“We developed the Flex technology, which allows us to design flexible bottles with shape memory, and new necks that further lightweight our bottles,” says Franck Hancard. “The design of the preforms is also changing – they’re easier to heat, which helps us to produce lightweight bottles. But what also makes new design possible is the evolution of the machines. Some bottles couldn’t be produced on older equipment. Bottle design and production are really closely linked.”
There’s no denying that producing a 6.6g bottle is an incredible feat, but will we ever see such a lightweight bottle on supermarket shelves?
To date, Nestlé Waters North America’s 12.3g bottle, which was developed in collaboration with Sidel and Husky for its Pure Life brand, is the lightest bottle on the market.
Krones is still looking for a customer willing to take the 6.6g concept bottle to market, saying: “Until now it’s only in the concept phase. We’re looking for a customer for implementation.”
Perhaps one reason brand owners aren’t exactly falling over themselves to adopt these ultra-lightweight containers is because they stretch the definition of the term ‘bottle’ to the point where they’re barely recognised as such.
Nextek managing director, Edward Kosior, says: “There are bottles of 10g or 11g which are commercially viable. They’re quite delicate to hold, so there could be overspill if a consumer grips them tightly. However, when you get down to 6g, you’re talking about a completely different concept. How to handle them for example? You can’t hold onto the body and open them with a conventional closure. You’ll squeeze them too much.
“When you get to that level, there’s a whole range of other competitive technologies as well, because once you move away from the concept of a rigid package that’s resealable and puncture-resistant and can stand unsupported, you’re moving to a bag concept. Consumer thoughts about that may well shift and the market may not be there, though it’s technically feasible.”
Krones points out that such containers are in fact already in use in Nigeria, where Nestlé is selling water in 50cl Plocs (Plastic Low-cost Ovoid Containers) weighing 4.5g.
However, echoing Kosior’s view that although technically feasible, such lightweight containers may not be what the manufacturer or the market wants, Schau says: “This bottle design cannot be handled on a standard high-speed line without major modifications. Most probably it’s also not what most brand owners want for their product. The Nestlé example shows very well that it depends on the technology used and what the brand owner or his customers demand from the bottle.”
So does this mean we’re nearing the limits with lightweighting?
According to Husky, there’s still scope for more widespread adoption of lightweighted bottles. “If we look at the lightest water bottles on the market, they represent a small percentage of all bottles in the world,” says Reynolds. “Most bottles are still much heavier, so there’s significant potential to reduce resin usage.”
However, he points out that trying to get every bottle down to the lightest weight isn’t the goal. “Each application is unique in its performance requirements due to differences such as filling equipment, cappers, shipping distances and conditions.”
In terms of pushing the envelope to produce lighter bottles, most in the industry seem to think the technology has almost reached its limits.
Krones says: “We’re close to the limit, but we still have to find out how close,” while PET Engineering says: “For the moment, the limit is due to the available technology. We’re working to push the limit and to reduce the weight.”
Kosior suggests that lightweighting limitations are rooted not so much in design constraints as in brand owners’ understandable reluctance to invest in new equipment when there’s nothing wrong with existing kit.
“A lightweighting exercise with the major beverage companies found that while they’re working towards reducing the weight of their 50cl bottles by around 1g, they could take 2g off if their machines were replaced with new technology,” he says. “They’re living with older machines which limit their capacity to exploit advancements.”
For companies keen to boost their green credentials, Kosior suggests that incorporating a percentage of recycled content into bottles is a better way to go.
“The use of recycled content is the fastest way of reducing the carbon footprint of any bottle,” he says. “You can reduce weight, but you’ll only achieve a carbon footprint reduction in proportion to that weight reduction, whereas if you incorporate recycled PET (rPET) into your bottles, you’ll get a far greater reduction with no change in the actual container structure.”
Another reason rPET is more environmentally friendly than ultra-lightweighting is because, when bottles get very light, they cannot be recycled.
“In a plastics recycling plant, bottles that are in the order of 20g are a sensible material to recover, but when they get down to 10g, they become harder to capture because they can’t be unscrambled and sorted by conventional means. So a high proportion of those bottles ends up in landfill,” says Mr Kosior.
That said, incorporating rPET into water bottles isn’t without its problems. As Reynolds says: “The use of rPET for producing new bottles presents a number of challenges, including clarity, yellowness, black specs, and often an increased frequency of blowouts during blow-molding. When you’re dealing with lightweight water bottles, the problem becomes even more pronounced. Husky is currently working on product line enhancements to enable the use of higher amounts of rPET with fewer problems.”
According to Sidel, the challenges of using rPET have more to do with material availability. “The challenge isn’t really technical,” says Hancard. “The biggest challenge is the PET collection: today there isn’t enough collected PET for both textile and beverage market needs.”
Ultimately, whether manufacturers choose to press on with lightweighting or follow in the footsteps of Evian to produce containers with a percentage of recycled content, how far they can go has much to do with how serious their consumers really are about the environment. Are consumers prepared to sacrifice container rigidity and aesthetics to save the planet, and are brand owners willing to take the chance that they are?
Lynda Searby is a special technical feature writer with a broad knowledge of the food and beverage industry.
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