PETpla.net Insider 09 / 2012

CAPPING / CLOSURES 40 PET planet insider Vol. 13 No. 09/12 www.petpla.net Co-injection keeps oxygen at bay Barriers under control Fig. 1.: This 38mm hot fill polypropylene (PP) beverage closure includes a tamper-evident band at the bottom, a locking band, bottle support on the sides, a plug seal, and a co-injected 0,1mm oxygen and CO 2 barrier layer made of EVOH (illustrated here in blue). This barrier has 30 times more resistance to permeation than a monolayer polypropylene cap. The new approach produces a single piece cap ideally suited for products like carbonated beverages, juices, water and tea that need oxygen or CO 2 barrier protection. The cap also has a tamper evident band compat- ible with current market bottle fin- ishes. This tamper evident band fea- tures a continuous conical locking band with ribs to position the locking band on the bottle finish. Design by purpose These co-injection results are obtained by precise, integrated control of dosing, flow and pressure of the two melt streams. Balanced filling of 3-5% barrier-layer mate- rial into all parts equally is achieved using proprietary iFlow manifold technology, precise control of the E-Multi unit, and the positioning of the valve pins using the E-Drive actuation system. The single inte- grated Iris control system controls the E-Drive pin positioning, hot runner heaters, and the barrier injec- tion flow to ensure that the elements of the system work together in har- mony. The E-Multi auxiliary injection unit also allows moulders to revital- ise existing machinery by convert- ing a mono material machine into a multi-material application. The proprietary and patent- pending Iris co-injection system design moves the melt simultane- ously in the primary and secondary injection flow paths and delivers it through a single gate (Figure 2). The Iris nozzle design merges the two melt paths together and allows for on-the-fly control of the barrier position both in the direction of flow and in the cross section of the part. With a single integrated control- ler, the moulder can observe and control what is happening in the melt streams to a greater degree than ever before. Beverage barrier closures A recently showcased 16-cavity mould (Figure 3) produces the parts that are a tamper evident, liner-less, hot fill HDPE cap for a beverage container with an integrated oxygen and CO 2 barrier. The patent pending, tamper evident band is compatible with current market bottle finishes. The band features continuous coni- cal locking, with ribs to position the locking band on the bottle finish. The co-injected barrier material is EVOH. Using Mold-Masters new Iris co-injection technology such caps are moulded with barrier technology encased in its centre. This results in a simpler cap design that can be used directly as opposed to need- ing a secondary operation to insert or mould a liner. The simultaneous injection of 3 to 4% barrier into the 16 cavity production mould is result- ing in a very balanced thin layer. Fig. 2: The Iris co-injection system: The Iris nozzle design merges the two melt paths together and allows for on-the- fly control of the barrier position both in the direction of flow and in the cross section of the part. Fig. 3: The 16-cavity Iris system for 38mm hot fill polypropylene (PP) closure produces co-injected parts at a cycle time of less than 5s. The permeation of oxygen into beverage containers or carbon dioxide out of carbonated products has a negative impact on product quality and shelf life. There has been consider- able emphasis and development on beverage containers in recent years to reduce this per- meation. Mold-Masters’ latest co-injection development now enables caps to be produced with a co-injected barrier (Figure 1).