A Process for On-Line Quality Control of Recycled Plastic Flake

Generally, it is accepted that for plastics recycling to be economically viable in the long term, recycled resins must be competitive with virgin resins. To compete with virgin material, new applications must be made available for recycled resins. Such applications will require that the recycled resin be of a high purity level. Thus, many processors are requiring ever-tightening contamination limits in their recycled resin products. With these tightening contamination limits comes the need to remove contaminants from the stream that do not come from whole bottles or that get through whole-bottle detection systems. Unfortunately, automated flake sorting for the entire stream of material is too expensive for many processors. Current quality control methods require that small samples be taken manually from the stream after processing and manually analyzed in the laboratory. This requires several hours before the quality control results can be obtained - at this point, the material already has been placed in the storage area. Unacceptable contamination levels, therefore, will have contaminated entire gaylords or even a silo of material before the processor is aware of the problem. The processor then typically will blend the contaminated material with pure material, resulting in a lower quality product. The Phase I objective is to determine the feasibility of developing a rugged analytical system for online quality control that would continuously monitor a sample from the recycling process material stream to determine contamination levels in real time. When the contamination level is too high, the system would activate a diverting mechanism so that contaminated material is diverted away from the main stream of material for further processing.