Film extrusion
Packaging films produced by film extrusion make up a significant proportion of plastic packaging produced worldwide.
In Germany alone, around 2.3 million tons of foils with a sales volume of 6.8 billion euros were produced in 2015. This means that foils make up 51% of the plastic packaging produced.
Thermoplastic granulates formed into films by extrusion can be found in a large number of film articles for consumers:
Agricultural films, baked goods packaging, construction films, stretch hoods, ice packs, film packaging for meat and poultry, fresh goods packaging, household bags, industrial films, lamination films, garment bag films, medical films, packaging for dairy products, garbage bags, garbage bags, fruit and vegetable bags, shrink hoods, heavy-duty bags, shrink wrapping films, heavy goods bags Frozen products, animal feed packaging, carrier bags, outer packaging, shipping envelopes, goods bags, diaper films, newspaper film ...
Manufacturing
In terms of process technology, a fundamental distinction must be made between blown film and cast film extrusion, also known as cast film extrusion.
The extruders and peripheral units for plasticizing the thermoplastics are roughly the same for both manufacturing principles.
The nozzles from which the plastic melt exits the extruder and the downstream processing units and steps are fundamentally different.
With blown film extrusion , the melt emerges from an annular nozzle in the form of a closed film tube, which is discharged upwards towards the hall ceiling. The film is biaxially oriented as it exits the ring nozzle and the cooling air inflates the hose.
In cast film extrusion (cast film extrusion), the melt emerges from a slot die and is cooled on a cooling roller and processed further parallel to the hall floor. The film is oriented monoaxially between the exit from the slot die and the contact with the cooling roller.
With the cast film technology, other materials, such as. B. paper or aluminum foil, coated with thermoplastics .
Individual evidence
- ↑ IK Industrievereinigung Kunststoffverpackungen e. V.
- ↑ Andreas Limper, Process Engineering of Thermoplastic Extrusion, Hanser (2012) - page 271 ff.