PETpla.net Insider 12 / 2019

PREFORM PRODUCTION PET planet Insider Vol. 20 No. 12/19 www.petpla.net 14 PREFORM Special A review of preform developments When designing preforms, a number of parameters have to be defined, like the overall shape, the neck finish and mechanical and barrier characteristics that need to be achieved. The length of the preform results from the bottle’s height (minus neck) as well as the axial stretch ratio, while the core diameter results from the Hoop stretch ratio and the bottle’s diameter. The preform wall thickness results from the bottle wall thickness multiplied by the biaxial stretch ratio. To produce PET bottles, preforms have to be manufactured and stretch blow moulded. Both processes can be carried out independently using differ- ent machinery (2-stage process) or in a single-stage process. In the 1-step or single-stage process, PET resin is melted and moulded into a bottle in one machine, using residual preform heat from the injection or injection-compres- sion process to blow mould bottles into an equal number of blow cavities. In the 2-step process, preforms are manufactured on injection moulding machines as a first step by melting and moulding the PET resin. The finished preforms with a complete neck can then be re-heated and stretch blow moulded into bottles in stretch-blow moulding machinery in a second step. In 1995, Nissei ASB developed the 1.5 step moulding method, in which preforms are injection moulded, partially cooled to maximise stability and then temperature conditioned before being passed to a blow mould. This blow mould usually contains a third of the number of cavities of the preform mould (as it takes three times longer to injection mould preforms than to blow bottles). Each process has its advantages and disadvantages in terms of output or flexibility (amongst other factors), and preferences changed over the years. Enjoy the journey through 20 years of PET preform developments, the last topic of our jubilee year series! First of all, a look back over the past 20 years: What developments have been particularly influential to your activities in the area of design/system manufacturing for preforms? Moraldo Masi, PET Business Director Closures, Containers & PET BU Sacmi: “For many years the main driver was product light-weighting, one of the pillars of environmental protection and sustainability. Then, the focus broadened and achieving a circular economy became another tool for reaching real sustain- ability and protecting the environment. Everybody is working on new development based on re-use/re-cycle of products; we changed our designing drivers towards this new perspective. I believe that this is extremely positive and a big opportunity for companies strongly involved in PET products manufacturing systems, due to the fact that PET is the only fully multiple recyclable polymer and has perfect physical and mechanical features to make packaging.” Pablo Fiorentini, Global Sales Director, Preform Systems & Tooling Sipa: “As producers of preform systems, our main focus has always been trying to increase production capacity per installed unit with consequent benefits in terms of energy consumption and CO 2 emissions. Flexibility is our key word, we give customers complete freedom of choice thanks to the very high level of compatibility of our Xform Preform machines with moulds of different generations and different manufacturers. Always focused and attentive to the environmental impact of the industry to which we belong, we work tirelessly to propose ever lighter container solutions that meet the expectations and specifications required by our customers. Developing lighter preforms and thinner walls leads to multiple benefits, including a reduction in the total volume of processed PET, a reduction in cycle time, a reduction in the energy required to cool down the preform itself and a drop in the thermal power required during the heating process inside the blowing machine ovens.” by Gabriele Kosmehl