manufacture of stretchwrap film using pib masterbatch
cast film
we would like to suggest how you can best make stretch film for pallet wrapping, using our pt-60masterbatch on cast film lines.
blend 2 to 4 % by weight of pt-60 pellets with 98 to 96% of polyethylene. Mix thoroughly in a ribbon or tumble blender so that the blend is uniform.
lldpe resins with hexene or octene comonomer are typically used for pallet stretchwrap film because of their excellent elongation and tensile properties. None of the resins to be used must have any “slip” agent or “antiblocking” agent. This is very important, as the presence of any such additives will destroy the cling properties of the film. For initial trials, no re-cycled resin should be used.
cast film is usually a multi- layer film process with 2 or 3 extruders. The cast film process typically gives film with a lower crystallinity and more amorphous quality than blown film, so pt-60 needs only to be added to skin (inner and outer) layers. Multi- layer cast film is ideal for one-sided-cling pallet stretchwrap where pt-60 is added to the inner skin layer (the layer that comes into contact with chill roll) at 2-3%.
a suggestion for the temperature profile of the extruder (using pt-60) is as follows:
first zone : 275°c
second zone : 280°c
third & fourth zones : 280-300°c
die zones : 290-310°c
the film should be trimmed just before the wind-up rolls. The tension on the rolls should be low, such that they are not wound too tightly or they will bunch-up at the ends and telescope when stored. If too loosely wound, the rolls will hump in the center and sag when stored on end. Some cling will develop during wind-up, but the maximum cling effect will take place during the 72 hours after production.
storage of rolls should neither exceed 35°c nor drop below 7°c if possible.
if you follow these directions, it should help you to achieve an excellent stretchwrap, with a higher degree of clarity and cling property.
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