Most single-serve plastic bottles for water, soft drinks, and juices are made of a plastic known as polyethylene terephthalate, or PET. Tens of billions of them are produced every year, and most of them have to be labeled—usually with pressure sensitive or shrink sleeve applications. The addition of labels can complicate recycling when the bottles enter the PET waste recovery stream.
In Germany, KHS GmbH has come up with a way to print directly onto the surface of PET bottles using a process that it says does away with the need for labels in the first place. The company, a producer of filling and packaging systems for beverage, food, and non-food products, has a prototype method for applying CMYK, white, and spot-color color UV inks to PET containers at an optical resolution of 1,080 x 1,080 dpi. The inks cure instantly and do not bleed into the structure of the PET, which is porous.
The result, says KHS, is a brilliant color image that will stand up to wear and tear on the filling line, in transit, and in the hands of consumers. The low-migration UV inks have been found safe for food packaging and do not interfere with PET recycling, according to the company.
Printing directly on PET instead of labeling is said to shorten time to market, cut material and logistics costs, and reduce CO2 emissions. KHS reckons that if a labeling machine applies 36,000 labels per hour on 220 days of the year in two-shift operation, switching to its direct printing system will save about 60 metric tons of label stock and adhesive.
The bottom line, according to the company, is that “labeling materials and adhesive are now completely superfluous” for branding PET containers.
NMP Systems GmbH, the KHS subsidiary that developed the process, incorporated it into an entry that won a 2014 German Packaging Award from that country’s Ministry for Economy and Energy. The winner, Nature MultiPack™, consisted of directly printed PET bottles held together in a group by dots of adhesive instead of a film overwrap. Individual bottles are removed by twisting them away from the rest of the pack.
Substituting this system for film wrapping uses up to 85% less packaging material and saves up to 67% energy during production of multipacks, says KHS. The system can be applied not only to PET bottles but also to glass bottles and cans.