According to Plastic Products, Plastic Waste and Resource Recovery, published by the Plastic Waste Management Institute, roughly 20% of plastic waste generated in our daily lives is recycled as material for new products (material recycling), while the remainder is used as fuel or incinerated. Recycled plastics have to maintain a certain degree of purity, which is why materials made of plastic waste, such as acrylonitrile butadiene styrene (ABS) and polypropylene (PP), must be accurately identified.
However, black plastics, often used in home electronics or automobile upholstery, do not transmit or reflect visible light, making it difficult to identify their materials using conventional near-infrared spectroscopy. Additionally, in order to accelerate plastic recycling, higher accuracy and productivity are required for sorting operations.
Canon's new product employs a proprietary tracking Raman spectroscopic method to rapidly sort all plastic pieces regardless of their colours, including black, with high precision, thereby helping to improve the productivity of recycling plants. Canon attributes the machine's high-precision, high-speed sorting of plastic (including black pieces) to its combination of Raman spectroscopy with a tracking mechanism.
Raman spectroscopy is a detection method that utilises laser light to illuminate plastic pieces to obtain molecular information of the substance, thereby enabling the material detection. This method is technically applicable to black plastic.
However, due to the limited amount of reflection by the black plastic pieces, the measurement time is too long relative to the speed and throughput required to effectively sort all the pieces regardless of their colours at recycling plants. Therefore, the practical application of Raman spectroscopy to sorting black plastic has so far proven difficult.
By combining Raman spectroscopy with Canon's measurement and control equipment, the company has developed a tracking Raman spectroscopy technology which scans laser light toward the pieces, thus ensuring there is enough measurement time required for each piece of plastic according to its colour and achieving high speed and high accuracy overall.
With this new system, the materials of black plastic pieces which were challenging to identify using the conventional near-infrared method can now be identified in a practical manner even when mixed with other colours, thereby helping to improve the productivity of recycling plants and, as the result, maximising material recycling.
Canon says its new product maintains a conveyor speed of 1.5m per second and can sort up to 1 ton of plastic per hour. It can even be customised according to a customer’s throughput and installation space by changing the module which tracks and measures the plastic pieces or the combination of conveyor belts.
