|
Home > MacroLetter > 6.1 - Autumn 2000 > Encapsulation - First Time in Blown Film
Encapsulation - First Time in Blown Film
Though encapsulation technology was previously developed for producing barrier films with PVdC in flat dies, it had never been achieved in blown film dies until now. Taking the initial encapsulated PVdC melt stream into the die and around its full circumference proved to be the most challenging part of the development process. The desired results were finally achieved through various sequential geometry changes in the flow channels. Macro has been awarded a patent for the development of blown film encapsulation.
Macro has recently sold two 20” (508 mm) 7-layer ATM MacroPack™ dies, one of them with encapsulation technology. The customer wanted a die that could produce Nylon-EVOH barrier film as well as PVdC barrier film. The system has 8 extruders (7 extruders for the 7-layer die + 1 encapsulation extruder feeding the encapsulation block). When producing PVdC barrier film a 9-layer structure is possible (7 layers from the die + 2 EVA layers at each side of the PVdC layer).
The benefits of encapsulation in blown film are not limited to facilitating the coextrusion of corrosive and easily degradable materials like PVdC. Difficult to purge resins like Nylon can be encapsulated in order to abbreviate resin changeover times thus improving productivity. Other benefits include the ability to produce a 3-layer film in an ABA structure using a single layer die.
|
