On an Aquarex film extrusion line, film is blown downwards, with water used to quench the bubble instead of air. Quenching the bubble with water rather than air increases the cooling time by a factor of 30, according to W&H. The sudden freezing of the melt minimizes the build up of crystallites in the plastic, leaving processors with an amorphous structure with high-end optical properties. Although the film is blown downwards and water is used to quench it, the biaxial stretching effect is maintained, and clarity is said to match that of cast film.
The line running during that open house was an Aquarex running a 3-layer, 200 µm, high-clarity PP film for the production of IV bags. The clarity achieved with the water quenching is especially important for such applications. Plasticized PVC remains the material most used in this application but concerns about the effects of phthalate plasticizers are behind a push for non-PVC films suitable for use in these applications. Such concerns also have driven the development of and demand for non-phthalate plasticizers.
Aside from the optical properties, the water quenching process also improves mechanical properties, such as puncture resistance and dart-drop-value, reports W&H. Sealability is also improved on converted films, it adds. The manufacturer's PP film line for IV bags caught the attention of visitors from China, where PVC is banned from use in infusion bags, as well as processors in other regions too, said those W&H officials. Talks are still ongoing but the manufacturer expects the Aquarex line's showing during the open house could lead to some significant sales to processors of non-PVC IV bag films, among other applications. —MPW Staff