Filtration

There are several filters to filter melt before reaching the Die.

1) NSF/Cofit Filter-

This filter is used in Co-extruder to filter the melt of skin layer.

In which two cofit filters are there in this filtration system.

Which can be used single at a time or both at the same time, manual cleaning also can be done in this system.

(Inside pictorial view of cofit filter without melt)

(Inside pictorial viw of coft filter with melt)

2) LLF (Long Life Filter)-

This filter is used as main extruder filter, this provide a long and healthy run for plant,

so it is called Long life filter.

This filter has many components.

Note - Above shown figure is for example only.

Size of filter and no. of candles and rods may vary according to capacity of plant design

Material Flow -

The mixture of the PP-homopolymer and the edge trim fluff is melted in the main
extrusion unit and conveyed to the filter.
The filter is to retain contamination from the melt. This filter has a certain amount of
filter candles.
By using filter candles a large filter surface in a relatively small construction is ob‐
tained. Large filter areas provide long filter life and small pressure losses.
Then the melt flow continues from the filter to the die.
For coextrusion there are coextruders. They serve to melt and to convey the sealing
and intermediate layer material. Intermediate layer only for 5-layer layout.
The coextruders are connected with the die by the copolymer filter which consists
either of a strainer and various layers of filter fabrics, the so-called "filter package" or
has a certain amount fo filter candles.
The melt of plain film and coextruded film is discharged by a 3-layer/5-layer die. The
die distributes the melt stream or melt streams (in case of coextrusion) in even thick‐
ness across the total width.