MATERIALS / RECYCLING PETplanet Insider Vol. 23 No. 10/22 www.petpla.net 18 Masterbatch for hot fi ll packaging No compromise on processability A lot of food and beverage products require a long shelf life, so they require filling at high temperatures to remove harmful bacteria or microorganisms which might damage or interact with the product. Normally the hot filling temperatures range from 80 °C up to 90 °C, depending on the specific product. A special masterbatch has been developed to increase the crystallinity of PET without compromising its processability resulting in a considerable increase in thermal and oxygen barrier properties. Hot fill for PET bottles presents many challenges, starting from the thermal resistance of the material itself, to the resistance to implosion to avoid deformation and to the oxygen barrier properties to ensure a longer shelf life. The current hot fill technology available on the market use hot moulds at 140-160 °C. It is feasible with special blow moulding machines that have a specific blowing system capable of blowing through perforated stretching rods and systems of special valves that allow the recirculation of air to lower the temperature of the containers below 100 °C, with an increase in the cycle time. “This technology can be very effective but often it is not easy to have a high enough output of bottles, let’s say in excess of 5 million, to justify the investment in a dedicated special ISBM or SBM machine,” explains Giovanni Sonzogni, CEO and Innovation Director of GS4Plastic. “In addition, it is often necessary to use special hot fill PET grades with a high Tg, in order to guarantee a high thermal resistance, and this further increases the cost of the final packaging,” he concluded. The Italian start-up GS4Plastic SB detected the need for a process that allows the production of a hot fill packaging with a high thermal MATERIALS resistance and a good barrier property against O2 that can be obtained simply, cheaply and with low cycle times. GS4Plastic patented a special masterbatch called FastPET, that is claimed to increase the crystallinity of PET without compromising its processability; this results in an increase in thermal and oxygen barrier properties. It is possible to use FastPET for the production of hot fill bottles in single stage stretch blow moulding (ISBM) without the need to use special hot mould technologies. FastPET is added to PET or rPET in the feeding of the extruder together with other additives, such as pigments or others, says GS4Plastic. The recommended dosing percentage is lower than 1% in weight. Thus the bottles made with this special masterbatch are 100% recyclable in the existing PET supply chain. With FastPET it is possible to make a monolayer container resist up to 88 °C, thus making it suitable for the hot fill process without either the use of special PET or expensive technologies, says the company. Increased shelf life by up to 12 months With the additive, it is possible to increase the barrier properties, and consequently the shelf life of the products by up to 12 months, states GS4Plastic. The increase must be evaluated based on the type of product and on the design of the preform/ bottle. ISBM tests with 3 or 4 stations, have been carried out, and in addition to confirming the increase in properties, a surprisingly significant reduction in the cycle time has been found. As an example, the start-up tested an 18 g bottle produced on a 4 station machine with a mould cooled to 13 °C with a cycle time of 17.5 s. It was found that with the masterbatch it was possible to achieve a cycle time of 15.5 s. The only disadvantage is the loss of transparency of the bottle. The masterbatch acts on the crystallinity of PET, and a slight loss of optical properties is therefore to be expected. The patented masterbatch called FastPET is claimed to increase the crystallinity of PET without compromising its processability.
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