Extending the Reach of Blown Film Encapsulation
Barrier resins like Nylon, EVOH, PVdC, COC and PETG are essential to food, medical and general barrier packaging applications. All of these materials, with the exception of PVdC, can be readily processed in commercial size dies (dies above 200 mm in diameter). Unfortunately, processing PVdC with commercial size dies is not so easy and has traditionally been restricted due to its thermal sensitivity – PVdC degrades easily, which is accelerated in dies with longer residence times (i.e. large, commercial dies). The resulting continuous interruptions of production to take the die apart for cleaning make the process economically unfeasible.
Through innovative encapsulation technology developed and implemented by Macro in the early 2000s, commercial scale processing of PVdC with blown film dies above 200 mm in diameter was achievable. Up until that point, encapsulation technology had only been developed for producing barrier films with PVdC in flat dies – it had never been achieved commercially, in large blown film dies.
During the course of development and improvement of this technology, Macro was awarded five patents for blown film encapsulation technology and for developing barrier film structures. Since then, Macro has sold several commercially successful multilayer blown film lines with dies up to 500 mm in diameter that utilize encapsulation technology.
In general, these lines can produce PVdC-based barrier films (PE/tie/Encapsulated PVdC/tie/PE) from 25 microns to 225 microns. The thinner gauge films (25 microns to 100 microns) can be used as barrier sealant web to be reverse-printed or laminated to the surface of BOPP, BOPET and BOPA films for VFFS and HFFS applications. Alternatively, this barrier sealant web can also be laminated to rigid substrates, such as PVC, APET, PP or HIPS sheets for rigid thermoforming applications.
After developing the encapsulation technology for PVdC it was observed that the benefits of encapsulation are many and can be extended to other barrier materials. For example, Nylon takes an inconveniently long time to purge from the die when frequent order changes for a processor are necessary. By encapsulating Nylon with a suitable tie resin the nylon melt does not contact the die surfaces, leading to cost savings through faster changeovers and reduced consumption of purge resins.
Encapsulation technology is well suited for EVOH processing as well. To achieve optimal results, long residence times should be avoided. By encapsulating EVOH with suitable tie resins, the EVOH is prevented from entering slower moving areas of the die that occur near the die surfaces. Subsequently, the residence time is significantly reduced to produce superior barrier films.
For barrier films that require the barrier properties of EVOH and the puncture resistance of Nylon, this encapsulation technology can be used to encapsulate EVOH using Nylon (copolymer) to make a Nylon/EVOH/Nylon structure. This means on a 7-layer blown film line, one can produce a 9-layer film structure without increasing capital costs.
Macro's encapsulation technology is commercially available on all its blown film lines (and cast lines) and popular among those who have already purchased and are using this technology. Because of the versatility of these lines, Macro's customers are reaping the benefits of a line with the ability to process all of the three key barrier resins (EVOH, Nylon and PVdC) using the same extruders and die mandrels.