Coca-Cola's barrier technology to double PET shelf life

Just as this issue was about to go to press, The Coca-Cola Company announced a stunning development, BESTPET(TM) (Barrier Enhanced Silica Treated polyethylene terephthalate).


Atlanta-based Coca-Cola's patented BESTPET technology applies the clear colorless silica coating by vacuum process to the exterior of PET bottles. Presumably an exterior coating will make the technology easier for the Food & Drug Administration to swallow. Depending on bottle size climate and the temperature that the bottle is stored a product's shelf life as measured by loss of carbonation can be doubled. That's according to Tim Garnett Coca-Cola's vice president and director for engineering development.

The company has formed a partnership with Krones AG (Neutraubling Germany) and Leybold Systems (Hanau Germany) to further develop and commercialize BESTPET. Coca-Cola developed the BESTPET technology by working with what a company press release refers to as "leading German scientific institutions."

In an exclusive interview with Packaging World Garnett says Coca-Cola "has developed a prototype machine that's operating in central Germany and is capable of speeds of 3 bottles per hour." It's believed that the coated PET bottle being lab-tested in Germany is a 500-mL size. He says that while that machine is still being tested a new machine based on the prototype is being constructed for commercial returnable bottles.

"Our estimate is that the first commercial production on the new machine will be during the first quarter of 2000" Garnett relates. "We're still going through a selection process to determine where it will be used but our initial choice will probably be somewhere in Europe." Commercial bottles treated with BESTPET could be on U.S. store shelves by late 2000 but he says that's speculating.

Garnett adds that the technology could be used for the Coke's contour bottle "though it can work with any shape. The shape doesn't matter." As for which brands the answer is also open-ended. "It can work with Coke Fanta Sprite and other company products."

"We've formed a unique partnership" says Garnett. Krones AG supplies bottle handling equipment including conveyors and a "load-lock starwheel" while Leybold provides the bottle coating chamber vacuum system and plasma-generation process.

Looking to perform the coating process at speeds of 20 bottles/hr he says "that's where Krones came in. Krones is among the world's best when it comes to package handling technology and they've developed that for [this process]."

The continuous process begins as the blow-molded bottles are conveyed single-file to the rotating starwheel. Developed by Krones the starwheel uses mechanical grippers to pick up bottles by the neck. As the starwheel rotates it delivers bottles into the enclosed vacuum chamber. The bottles are transferred to another conveyor system that runs inside the vacuum chamber. This conveyor also grips bottles by the neck.

Garnett says that in the chamber vacuum draws air out of the bottles and the surrounding area in the chamber. "The bottles do not collapse as long as the pressure is equal inside the bottles and externally. It would be a problem if you drew air only out of the bottles but not out of the surrounding air."

The conveyor holds the bottle by the neck at an angle so that as each bottle is conveyed in a U-shape track through the chamber the coating is evenly applied to the sidewalls and base. The bottle also rotates as it moves through the chamber to facilitate even distribution of the silica.

Two electron guns are positioned at the bottom of the chamber. The guns help to evaporate the heated elemental silica shaped somewhat like pebbles. As the silica evaporates it forms a plasma cloud that rises to coat the bottles. The coating thickness Garnett estimates is "between 30 and 50 nanometers--it's very very thin."

Since the bottle is held at its neck area its open top is screened off by the conveyor system so that the bottle finish and interior are not coated. After coating bottles cure instantly he says before they're transferred back to the same starwheel. The starwheel discharges bottles onto a conveyor. Coated bottles may then be palletized and sent to a bottler later or fed directly to a filling line.

"This coating basically doubles the shelf-life of our current packaging" Garnett states. Specific shelf-life differences between silica-coated bottles and uncoated bottles vary depending on bottle size the general climate and if the bottles is kept cold during the distribution process. "But typically the shelf life for soft drinks in a PET bottle is around 10 weeks for us and this process doubles that." That provides a competitive advantage for Coca-Cola he says.

But when asked if this additional shelf life could help the company consolidate its bottling operations the company said that would be speculative to say. No firm decisions have been made yet on whether this process will be completed by a molder or at a bottling facility. "The most efficient way to do it is immediately after blow molding and that's our preference" but he says several factors are involved in that decision since the company uses a variety of suppliers to mold the bottles.

Garnett says the process does not affect decorating possibilities and won't result in any consumer upcharge. From Coca-Cola's perspective he admits that the process "does add cost. But compared to competing technology we believe it's lower. The cost of the elemental silica is a nonevent. The real cost is the depreciation of the capital cost of the equipment. So when you ask how do we plan to recover the cost it's really through the ability to grow market share and volume."

Besides potential sales Coca-Cola might be able to justify the added costs through lightweighting. The coating Garnett says adds less than 1g of weight per bottle depending on bottle size. "We've been experimenting with lightweighting and there is the potential for that. We expect to know more by early next year but we could lightweight anywhere between five and 10 percent and that's a considerable savings."

Coca-Cola is also using a third party to test for the coated bottle's recyclability. "We need to conduct more extensive tests with the major recyclers and we plan to do that by the end of the year" Garnett notes. "But our preliminary tests are very positive and have shown there is no issue when it comes to recycling because we're talking about very small amounts of sand or glass."