Ultrasonic welding enhances recyclability of to-go cups
Iranpolymer/Baspar The production of sustainable food packaging such as beverage cups still offers great potential for optimization. This is demonstrated by the innovative solution of a start-up from Latvia. The company not only produces the cups for coffee to-go and soft drinks from recycled PET, but its production technology also ensures that the foamed rPET used can be recycled again and again as a mono-material. The ultrasonic welding of the cup bases, for which Weber Ultrasonics has developed a product-specific welding solution, makes a significant contribution to this.
Coffee to go or soft drink – the drink on the go enjoys great popularity around the globe. One problem, however, is the beverage cups. Until now, they have usually been made of plastic or paper laminated with a plastic coating. These are materials that cannot be recycled or can only be recycled to a limited extent and therefore end up in landfill sites or incinerators. Sergey Nikitenko, founder of the FORPET project and one of the managing directors of FORPET Baltic SIA, wanted to do something about this. “The whole thing started with the idea of producing packaging for the food industry from recycled polyethylene terephthalate (PET), known as rPET,” explains the packaging expert.
rPET in food-safe virgin material quality
In discussions with various companies from the fields of plastics recycling and extrusion technology, the entrepreneur gathered information about useful system combinations for the project. In the process, he became aware of the innovative Liquid State Polycondensation (LSP) process from NGR.”With this technology, we can process PET flakes from recycled material into rPET in food-safe virgin material quality, which is certified according to the BRC Global Standard for food safety. The material can be foamed and can also be printed very well with water-based dyes and recycled as often as required,” explains Sergey Nikitenko. In the next step, another technology partner, extruder manufacturer Leistritz, was found for the further processing of the prepared material into films and sheets of varying thicknesses. Tests carried out in parallel showed that the rPET can be shaped like conventional packaging materials. It is therefore an ideal material for food packaging of all kinds as well as for blister packs, containers and much more.
Beverage cups as the first product
The first product chosen was to-go cups, for which a production line including an LSP machine and extruder system was first set up at the Latvian plant. There was still one hurdle to overcome. While the side seam of the cup is traditionally welded using ultrasound, a glued connection was required to integrate the base. However, adhesive would have been a second material, which would also incur additional costs. An alternative that could be integrated into the processing system was therefore sought.
Product-specific development of the ultrasonic welding process “Ultrasonic welding seemed ideal for our mono-material packaging. However, we needed a partner with whom we could work out an optimal solution. Initially, it looked like we would need three welding systems to join the base of the cup to the cylinder due to the geometry,” reports Sergey Nikitenko. During an internet search, he came across Weber Ultrasonics AG, an internationally active manufacturer of ultrasonic components for welding, cutting and cleaning. “In the first video conference, the company impressed us with its very professional and solution-oriented approach. During our first visit, we were then able to carry out direct tests with our material in Weber’s application technology center,” recalls the Managing Director. “We then set about jointly developing and adapting the ultrasonic process to the specific product.” A small design change to the base of the cup by the ultrasonic application specialists meant that it could be reliably welded with just one ultrasonic welding system in a welding time of 150 milliseconds. At the same time, the process is very energy-efficient.
Welding process with integrated quality control
The welding solution integrated into the production line at FORPET consists of two sonotrodes, adapted converters and oscillation units, as well as an Industry 4.0-capable welding generator Sonic Digital HS3 with 2,000 watts of power, which comes standard with five welding modes. Innovative functions ensure maximum process reliability. For example, the teach-in function automatically determines the optimum starting frequency and control parameters of the connected oscillating system. The Sonoscan function identifies the correct working frequency. The temperature tracking function calculates frequency shifts caused by temperature changes and also compensates for these automatically. Furthermore, the process parameters are captured in parallel with the welding process and transmitted to the higher-level machine control for evaluation. If there are any deviations between the current and stored, validated parameters, these cups are ejected accordingly. This ensures that only 100% leak-proof products leave the factory. For packaged foods, such as beverages, wet pet food, and salads, the vibration during the welding process ensures that any product residue present at the connection points is displaced, thus creating completely sealed packaging. This prevents costly waste.
Production to be expanded
With the first line, FORPET has been producing over 1.5 million to-go cups per month at the Latvian plant. Production here is to be expanded. Additionally, a second plant is planned at a different location. “The support from Weber Ultrasonics has helped us to do everything right from the start to establish a genuine circular economy for sustainable packaging products made from mono-material plastic,” concludes Sergey Nikitenko.
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