How plastic bags are made – Transcript of video –
“The plastic bags we use everyday are made from granules of linear polyethylene resin that will be melted. They combine the linear polyethylene with another low density one in this mixer. The granules are perfectly blended into a homogenous material. Granules melt in the extruder which heats them to a temperature varying between 180 and 240 degrees centrigrade. This produces a film of polyethylene in the form of a tube. It is several hundred meters long, has a minimum thickness of 37 microns and a circumference of 51 centimeters. The plastic tube gradually cools down. Rollers then flatten out the plastic tube. The polyethylene film is now easy to work – and now they cut the tube on two sides to obtain different roles. This knife then cuts the film to the required width. The excess strip is salvaged in this tube. Several hundred meters of film are produced and rolled out. This particular roll contains the required quantity of film. When the roll is full, the film is cut. This roll moves forward and can be transported to another department. An empty roll begins to fill up automatically. A full roll weighs 158 kilograms and can produce 35 000 bags. The next step – printing on the bags. This alcohol based ink circulates continuously to retain its viscosity. Impressions are made by inking rollers. Here another colour is being applied on the bags. Once printing is over, the plastic film is rolled up again. The roll in now full and the cutting of bags can get started. This machine makes 150 bags per minute. A sealer bonds the edges of the bag together with heat. The wheel picks up the bag and puts them on two spindles that can hold 250 each.
Here they are making bags with a hermetic zipper. The zipper is made from a plastic pad which inserts into a slot. The zipper is made in advance and is unrolled progressively. The zipper strip is cut and heat bonded to the bag at 180 degrees centigrade. And here’s the zippered bag all finished.
In this other department of the plant, they make plastic bags with handles. Printed bags circulate on these rollers. The machine that welds
the sides gives the bags the desired shape. Then another machine with a punch cuts the handle holes. Bags are heat sealed and cut at 150 degrees centrigrade.
Here they fabricate another product – packaging bags. One end of the bag is heat sealed. This machine makes holes which let air out of the bag when it’s being filled to allow then to be generously filled with items. At this stage a stamper cuts the handle holes. Bags are cut to the required size, automatically sealing the other side of it. This plant makes 8 types of bags for an overall total of just over 1 million a day.”