Manufacture covers a coextrusion castfilm line for the machine
stretch film rolls. The raw material used for the extrusion process is
Linear Low Density Polyethylene, LLDPE in short. Three extruders
called A, B and C form a three layer, asymmetrical film structure
called A - B - C.
The core layer is typically around 56% of the total thickness of the film
while the outside layers form 13% in case of layer A and 31% in case
of layer C.
Outside layer A:
Layer A, the non-stick outside layer runs on a LLDPE C6 resin.
Since this layer is not sticky it ends up on the outside of a wrapped
pallet making it easy to move pallets along side each other.
Core layer B:
The core layer consists of a blend of virgin resin and reclaim material
generated from edge trimming. For hand roll qualities LLDPE C4 is
commonly used for the core layer.
Outside layer C:
Layer C, the cling layer works with a blend of VLDPE (very low density
LLDPE) and a standard LLDPE C4.
The ratio of this blend is typically 25% VLDPE and 75% LLDPE C4.
The VLDPE enhances the cling properties of the film; it is acting as
a cling agent.
The line produces two in-line slit hands held and machine rolls of 450
or 500 mm width per roll. The maximum total net film width is therefore
1000 mm. The film itself is wound on 2'' and 3"" expanding air shafts.
The total thickness of the stretch film to be produced on the quoted line
is in a range of 15 to 40 pm.
Depending on the gauge typical operating line speed is from 300 to
500 m/min; the maximum mechanical line speed is limited to 600 m/min.
Total net output is 500 kg/h for gauges of 20pm and above. This results
in a name plate capacity of 4.000 metric tons per annum based on
a 24h /7 days operation with 8000 h available per year.
Due to the very short indexing time of the winder up to 400 hand rolls
can be produced per hour.
The line has an automatic core feeding system and a conveyor belt
to transport finished rolls out.