| How polythene is manufactured? |
Producing bags can be broadly split into 3 stages:

This first stage is to make polythene film. The virgin polymer
granules are blended with colouring agents (known as Masterbatch)
and other additives if required. This mixture of cold granules
is then conveyed to a film extruding machine, in which
the granules are heated until they are molten and again forced
through a die resulting in a vertical molten tube of polyethylene
tube.
This molten tube has air pumped into it,
so that it inflates like an elongated balloon. This stretches
the tube outwards, whilst at the same time the tube is being
pulled by a pair of nip rollers,
which stretch it the other direction.
The tube is cooled by cold air blowing onto
it; it emerges beyond the nip rollers, still as a flattened
tube (known as layflat tubing LFT)
is then wound on to a cardboard or plastic tube (known as
a core).
Being an ISO 9001
company, we have enforced stringent quality inspection measures
and have trained the operators accordingly who ensures the
correct width and thickness of the LFT. The finished rolls
of film, typically 50 kg each and of up to 100 metres in length
of tube depending on its thickness, are removed for the next
stage.
There are 2 main methods of making bags - sideways or lengthways.
i.
Sideways - with this method, the bags are produced
sideways-on by a servo driven convertor using a hot knife
to simultaneously cut and seal the tubular film to form the
sides of the bag, the bottom being the fold in the tubular
film. These are known as side-weld
bags.
ii. Lengthways
- using this method, the layflat tube is pulled through the
convertor and a hot wire makes a seal across the tube while
a flying knife (a sharp blade traveling at great speed), cuts
the film below the seal whilst the film is motionless for
the sealing process. Thus the seal forms the bottom of the
bag and the folds of the layflat tubing, the sides. These
are known as bottom-weld (or end-seal)
bags.
The entire process is automated ensuing high
level of accuracy
The
side weld bags are carefully wrapped in robust 80gsm Kraft
paper normally in 1000's whereas the bottom weld bags are
packed in strong cardboard boxes in 200's. All the packs are
then labelled, palletised and are finally ready for dispatch.
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