Extrusion International 2-2023

35 Extrusion International 2/2023 Blown film extrusion In this process the film is extruded vertically and wound into one flat tubular or two reels that are then converted by printing/coating/sealing into the final packaging product. Blown extrusion is typically for PE based materials, and the corona station is usually locat- ed at the top where the flattened tubular film is treated on the outside only. It is then split in two and can be ei - ther treated additionally, which is rare, or alternatively on the inside before being wound onto reels. On some extruders, the winder operates in both directions, so just one double-sided corona treater can be used. The reels are then passed through a converting pro- cess where the welding takes place, and as corona treat- ment is notoriously the enemy of welding, because the oxidation generated by the corona process weakens the welding area, it is important to evaluate the likely effect in each case. Blown film extrusion includes multi-layer polymers like LDPE, LLDPE, mLLDPE and MDPE, and applications include pallet hoods, collation shrink film, stretch hoods, lamination film, deep freeze film, heavy duty film, pro- tective film, and food packaging film. These are single layer up to normally 3 layers but can be up to 11 layers in the case of food packaging film Cast film extrusion In Cast film extrusion, the substrate is produced from a flat die and wound as a single film after being side trimmed. In this type of installation, the corona treater is usually located before the winder but after the first edge trimming zone. Because the edges of the cast film are thicker than the rest of the web they need to be cut off before entering the corona station and winder to prevent any damage to the rubberised rollers. Cast film extruders have a higher capacity and faster running speed than their Blown film counterparts, so a corona treater capable of delivering a higher power is required to achieve the best result. Cast Polypropylene, normally called CPP and different to stretch film, is used for a wide range of packaging, and normally requires corona treatment. If an oxygen barrier is required, the outer LDPE or PP layer is normally corona treated for the next printing or laminating process. Diaper film is typi- cally LDPE. How to get it right Extrusion is a composite process so there is a definite need for specialist knowledge to ensure the best results are obtained. As substrates become more complex to meet new packaging and safety criteria, the need for a detailed understanding of the surface treatment pro- cess and what it can offer becomes more important. With more than 70 years of experience and research data, Vetaphone is unrivalled in its ability to advise, educate and assist production personnel at every stage where surface treatment technology is required. Often misunderstood, it is a process that if managed correctly pays dividends throughout downstream processing from the moment of extrusion. Vetaphone A/S Fabriksvej 11, 6000 Kolding, Denmark www.vetaphone.com RECYCLING – CASE STUDY First PET Bottle-to-Bottle Recycling Line in Kenya T3 (EPZ) Limited, a member of Megh Group, ordered a Starlinger recoSTAR PET bottle- to-bottle recycling line for its new plant in Athi River, Kenya. With this project, T3 aims to contribute to the establishment of a circular economy with a positive impact on both the environment and the society in the country. D riven by the need to stop pollu - tion of the environment in the country, preserve natural resources, and increasing awareness about the benefits of recycling, the market for recycled PET in Kenya is growing. Megh Group company T3 (EPZ) Lim- ited is going to install the first PET recycling system for bottle-grade rPET and resin in Kenya and Eastern Africa, a Starlinger recoSTAR PET 165 HC iV+ recycling line, in Athi River just outside Nairobi. The food- safe rPET will be used in bottle pre - form production and for polyester fibre production in the textile and garment industries as well as for the group’s automotive trims and textile business Megh Singh Cush- ion Makers. T3 sources the post- consumer PET bottles for recycling through various collection strate- gies. With thorough collection and sorting methods and processing on the FDA and EFSA-approved Star- linger recycling system T3 ensures that the produced rPET resin will be of highest quality to meet the stan- dards of global brand owners such as Coca-Cola.