BLOWN FILM DIES | MACHINERY
Expansion plans: blown film dies
Refinements in blown film dies include stackable versions that avoid material degradation, designs for more effective production of barrier film, and versions that allow easy retrofitting
The sheer variety of film structures – and the need to produce it at speed – has meant that die designs continue to adapt to the demands of film producers. Macro Engineering has refined the design of its
Macropack co-extrusion blown film die, to create a version for the production of barrier film. Its latest version, called Macropack-FP, has a
stacked design in which each layer is fed by an extruder at a different centreline height. The main advantages of this design are: n The ability to incorporate temperature isolation – each layer can be processed at its ideal melt temperature and the die is especially conducive to running temperature-sensitive resins;
n The residence time in the spirals is equal, which reduces the degradation of temperature-sensi- tive resins; and,
n It can run less than 10% nylon on the outside, and the transition time from nylon to PE is up to three times faster than competitive stackable dies, says Macro. Macro has two previous designs of the die. Macropack-CP has a concentric mandrel design
where all the extruders are at the same centreline height. Macro says it has a low profile design – for shorter flow passages and reduced pressures – and a lower height for easier maintenance. It is able to run mostly polyolefin materials. It also offers a conical die design called
www.filmandsheet.com
Macropack-MPC. design. Again, the extruders are at the same centreline height. This design uses fewer bolts, which makes maintenance easier. For dies with diameters over 1m, this type of die has lower residence time (and less pressure) than the stackable design of the Macropack-FP – so the operational window can be increased. This die is suitable for agricultural and geomembrane applications. The dies were showcased at the recent NPE show in the US.
Layered performance Also at NPE, Alpha Marathon highlighted a number of its blown film extrusion technologies – including its patented Layer Sequence Alpha Dual Spiral System (LSADSS) dies, which it claims offer better performance through superior mixing and melt flow. The ADSS stackable dies provide high film quality by ‘doubling’ each layer. They are particu- larly effective in high barrier film packaging applications for food or medical films where more expensive resins may be used to achieve proper film characteristics, says the company. By combin- ing two layers per module the film produced per layer will yield improved performance. Because temperature isolation is provided for each module, a wider range of resin and film
June 2018 | FILM & SHEET EXTRUSION 41
Main image: Brampton’s Vector S air ring uses
segmented air to reduce starting gauge by up to 80%
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