PETpla.net Insider 11 / 2015

PREFORM PRODUCTION 17 PET planet insider Vol. 16 No. 11/15 www.petpla.net System with flexibility for overmoulding PET preforms Efficient barrier, high productivity In the production of two-layer preforms, the preform is transferred into a second cavity and overmoulded. Two-layer PET preforms, which are manufactured using the overmoulding technique, protect light- sensitive foodstuffs such as milk products from UV radiation where low levels of additives have been used. For the production of these preforms, Netstal have been offering a new PET line variant with two injection moulding units. With its PET-Line series, the Net- stal-Maschinen AG, Switzerland, has succeeded in establishing a proven high-efficiency production system for PET preforms on the market. A recent development which has become available is the new variant PET-Line 2C: this machine has been specially developed for the manufacture of PET preforms which are made up of two different components. Using this particular process technology, which is described as “overmould- ing”, preforms can be fitted with a thin, dark-tinted inner layer inside the injection moulding tool which provides a high-level barrier effect. In order to enable the overmoulding of preforms, the injection moulding machine has to be equipped with two injection mould- ing units and a special 2-component mould. For this the basic PET-Line machine has been extended by means of a second injection moulding unit as well as the necessary function- alities associated with the control. Savings in light protection additives Using the overmoulding process preforms can be manufactured that link a reliable light barrier with a low bottle weight and a high level of free- dom in terms of design. The bottles have proved themselves, for example, as a form of packaging for milk that has been subjected to ultra-high tem- perature processing (UHT). In the interests of circumvent- ing additional costs, the PRElactia technology operates with a two-layer preform structure. This involves manufacturing the internal layer from a grey-tinted PET material which is impermeable to light. It develops its full protective effect with a low propor- tion of additives of up to five percent. By contrast, the external skin of the preform is made up of white PET material. First a preform made from the material that is impermeable to light is injection moulded. After that this preform is transferred to a second cavity and overmoulded with the white layer. Afterwards an unloading device transfers the finished preforms to the aftercooling station. The PRElactia technology by comparison to single-layer preforms is the savings it offers in terms of light protection additives. Preforms that consist of one layer require a mini. of 15% additives, e.g. titanium oxide, to achieve an adequate level of protec- tive effect against the ingress of light. In the case of the two-layer preforms, the grey-tinted layer assumes the light protection function so that the propor- tion of additives in the preform is sig- nificantly smaller. As both layers are made up of PET, the bottles that have been manufactured using the PREl- actia technology can be assigned to a recycling process involving groups of identical materials once the utilisation phase is over. Low introduction threshold As a result of the possibility of switching between two-component and single-component preforms to suit demand, even smaller quantities can be manufactured economically and flexibly. In addition to overmoulding, the machines in the series PET-Line 2C are also suitable for the so-called coinjection process. In this the second material component is injected into the plastic core of the first component. This process variant may be used, for example, for equipping PET preforms with enhanced barrier characteristics. The coinjection technique also offers the potential for upgrading preforms with decorative effects. For example, it is possible to use differently tinted materials to produce preforms with attractive colour combinations. www.netstal.com The PET-Line 2C from Netstal is fitted with an additional injection moulding unit and is well suited to the overmoulding of PET performs.