Recycling Process
Sorting
Plastic scrap or waste comes in all manner of shapes and sizes such as plastic bottles, bottle crates, plastic pallets and car bumpers and a variety of material types.
Often these plastic materials are not compatible with each other when it comes to recycling so they have to be identified and separated.
It is also necessary to strip off any extraneous materials such as metal or foam which will hinder the recycling process at a later stage.
It may also be necessary to clean the scrap, particularly if the plastic waste comes from applications such as wheel bins, diesel tanks, etc.
Baling / Compacting
Across all sites we have the ability to compact soft scrap such as film or flexible products, such as flexible PVC.
This process is usually carried out to compact low bulk density material to a higher density to allow cost effective transportation to the point of processing.
Shredding / Granulation
Before the plastic waste can be melted down and recycled into plastic pellets for moulding into new products it must be reduced in size.
At its most basic this is a case of sawing large items of scrap so that they will fit down the throat of the granulation machines.
Shredding is a much more efficient way of reducing the size of large scrap plastic items. A shredder basically consists of a large tank that the scrap is fed into, at the bottom of which are heavy duty rotating blades which quite literally rip the plastic to shreds.
The output of the shredding process is irregular sized strips of plastic which will be up to several inches in length (still too big for the compounding process).
Granulation is probably the most common form of plastic recycling and there are many granulation companies dotted around the UK.
The process again involves a set of rotating blades, but unlike shredding the granulation process chips the plastic scrap. Screens are used within the granulation machines to control the size of the resulting regrind. Typically plastic regrind has a diameter of about 10mm which is ideal for the compounding process, although using smaller screens will produce a finer regrind that may be required by other processes.
Compounding
Plastic raw materials as regrind and additives are metered into a hopper at one end of a barrel.
This material is transported along the length of the barrel by a screw and is melted by applying heat from external heater bands, as well as the heat generated by friction / shear in the screw conveying process.
As the material moves along the screw, special sections of the screw knead, mix and compound the plastic and additives together. At the other end of the barrel, the melted plastic is passed through a fine wire screen that filters out any residual dirt, grit or other contaminants, and is then extruded through a die plate.
As the material comes through the die plate, it is cut into pellets and then cooled by quenching in water. It is then dried and packed into a selection of different packaging types.
