PETpla.net Insider 04 / 2010

PREFORM PRODUCTION 20 PET planet insider Vol. 11 No. 04/10 www.petpla.net optimisation to ensure close-contour mounting of the cooling sections wherever possible. Although manu- facturing moulds of this kind involves considerably greater expense, this is compensated for by a significant reduction in cycle time. A further effect was that the temperature required for the cooling water was increased by approx. 2°C with a simultaneous reduction in the amount of cooling water, whilst at the same time it proved possible to increase the difference in temperature between cooling water inlet and discharge. These steps led to energy savings in excess of 17% in the cooler unit. Cost effectiveness: reducing the cycle time In addition to the energy savings in relation to the PET system, achieving shorter cycle times is the key objec- tive since investment-hungry preform systems need to be used in the most efficient way possible. Netstal has taken this require- ment into account and presented the newly-developed Calitec aimed at an intelligent reduction of cycle time. Due to the fact that it is possible to seal the preform, still hot from the injection moulding process, in the neck area without damaging it and to support it with compressed air, significant savings and improvements have been made: the cycle time has been reduced by up to 20% whilst the quality of the pre- form has been enhanced. The Calitec system has already been installed on a number of occasions in Netstal systems with up to 192 cavities. Further systems have been installed in several European countries, and additional retrofitting packages or new machines with Calitec will shortly be ready for delivery. The efficiency of the Calitec System has been further increased by making use of more intensive cooling of the moulds as described above; as a result of the cooling, the outer skin of the preform becomes highly robust so that, even where cycle times are very short, Calitec sustains the cooling chain and thus prevents any reheating. This means that, with the new developments OH X-Cool (Otto Hofstetter) and HP- Stack (MHT), Calitec is able to demon- strate particular efficiency in operation, especially where preforms with smaller wall thicknesses are concerned. Overmoulding to the fore The Swiss company are also able to manufacture 2-layer preforms where the first layer can have a wall thickness of less than 1mm. This is made possible by means of a core support.The possibilities offered by this process could be considerable; worthy of mention are, for example, Prelactia (recently launched on the market) or various barrier applica- tions based on different raw materials (PS, PP) together with a wide range of colour applications. Since the launch of Prelactia this product has undergone consistent development.The composition of the two raw materials used, to which the necessary additives are added as early as the polymerisation phase, has been further optimised in order to elevate the light barrier. As a result of these endeavours success has been achieved in reducing the preform weight selected in the first stage from 28g for a 1l bottle to just 24g. At the same time the bottle did not suffer any restrictions either in terms of the bar- rier characteristics or in terms of the strength characteristics required. In the meantime, new Prelactia products developed for yoghurt or creamer pots have come on to the market. The product Prelactia received an award at the Emballage packaging exhibi- tion in Paris in the autumn of 2008. Further applications of overmouldings that may be of interest also include the use of recyclates on the outer layer of cap manufacture: by way of example, we would mention here 2-colour caps or the use of two differ- ent components. *Based on an article by Stefan Bock, Netstal Maschinen AG www.netstal.com Although Netstal may have not invented overmoulding, they apply the process for manufac- turing 2-layer preforms with high level reproducibility using this process. Prelactia received an award at Emballage 2008.