New Coca-Cola Barrier Method to Double PET Shelf-Life
Coca-Cola's patented BESTPET(TM) — Barrier Enhanced Silica Treated PET — technology applies a clear, colorless silica coating by vacuum process to the exterior of PET bottles. It is presumed that an exterior coating will make the technology more palatable to the Food & Drug Administration. 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 with BESTPET, says Coke.
Partnership Includes Krones, Leybold
The company has formed a partnership with Krones AG (Neutraubling, Germany) and Leybold Systems (Hanau, Germany) to further develop and commercialize BESTPET. Coca-Cola says it has developed the BESTPET technology by working with "leading German scientific institutions."
Coca-Cola says it has developed a prototype machine operating in Germany capable of speeds to 3,000 bph. The PW report says that the coated PET bottle being lab-tested is believed to be a 500-mL size. While the prototype machine is still being tested, a new machine based on the prototype is being constructed for commercial returnable bottles.
Coke estimates that initial commercial production on the new machine will be during the first quarter of 2000 and that it will probably take place somewhere in Europe. It is speculated that commercial bottles treated with BESTPET could be on U.S. store shelves by late 2000. The technology can be used for any shape of bottle, including Coke's contour bottle.
Krones AG supplies bottle handling equipment, including conveyors and a special load-lock starwheel; Leybold provides the bottle coating chamber, vacuum system and plasma-generation process. Through Krones' package handling technology, Coca-Cola is aiming at performing the coating process at speeds to 20,000 bph.
Continuous Process
The continuous process begins as the blow-molded bottles are conveyed single-file to the Krones rotating starwheel, which uses mechanical grippers to pick up bottles by the neck and delivers the bottles into the enclosed vacuum chamber. The bottles are transferred to another conveyor that runs inside the vacuum chamber, also gripping the bottles by the neck.
In the chamber, vacuum draws air out of the bottles as well as the surrounding area in the chamber. The conveyor holds the bottle by the neck at an angle so that as each bottle is conveyed 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 to help evaporate the heated elemental silica. As the silica evaporates it forms a plasma cloud that rises to coat the bottles with a very thin coating, estimated to be between 30 and 50 nanometers thick.
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 before being transferred back to the same starwheel. The coated bottles may then be palletized and sent to a bottler later or fed directly to a filling line.
Tim Garnett, Coca-Cola's vice president and director for engineering development, told PW, "This coating basically doubles the shelf-life of our current packaging. Specific shelf-life differences between silica-coated bottles and uncoated bottles vary depending on bottle size, the general climate and if the bottles are 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."
According to Garnett, the process does not affect decorating possibilities and won't result in any consumer upcharge. Although there is added cost in incorporating the coating, Coca-Cola believes the cost is lower than competitive technologies and that the company could justify the added costs through potentially increased sales and lightweighting.
Coca-Cola is using a third party to test for the coated bottle's recyclability, and, the company says, preliminary tests have shown there is no issue when it comes to recycling because of the very small amounts of sand or glass used.