The organic compounds that cause the bad smell of recycled plastics are found both inside the polymer matrix and on the surface of the plastic. In order to increase the quality of recycled plastics, a Spanish research group has developed a procedure and a system to eliminate these odours by extracting VOCs with water vapour.
This solution is based on the fact that extraction with steam favours the internal diffusion of volatile compounds due to the working temperature, as well as decreases the boiling point of volatile organic compounds immiscible with water, increasing their evaporation from the polymer surface to the gas phase and consequent removal.
The procedure for the elimination of odours in recycled plastics comprises the following stages and equipment (Figure 1):
a) Separation of recycled plastic material (P-VOCs) in an identification separation plant;
(b) Shredding of the plastic and reduction of the size of the plastic particles;
(c) Chemical washing of shredded plastic with surfactant in a stirring tank;
(d) Rinsing of the plastic material to remove dirt and chemicals used in stage (c);
(e) Drying of the rinsed material in a mechanical dryer;
(f) Deodorising the dry plastic material in a deodorising module where:
- the plastic material is introduced at the top of a distillation column;
- the steam from a boiler enters through the lower side of the distillation column;
- the plastic material falls by gravity along the distillation column, the plastic material comes into contact with the steam and the organic components are extracted from the plastic material by steam stripping;
- there is an outlet of organic product, comprising water vapour and VOCs, at the top side of the distillation column; and
- the VOC-free plastic exits at the bottom of the distillation column.
Apart from obtaining a clean product that is a plastic free of VOCs and odours (PL) that is reusable for other uses, it ends up generating an organic product (PO) that is also reusable, where there is water (FO-2) that can be used externally for other uses, and can also be reused to be recirculated to the boiler; and where there are organic (FO-1) remains composed essentially of essential oils that can be commercialized or reused as fuel for producing steam.
This process can be applied to plastics of varied nature (polyethylene, polypropylene, polyester, etc.) from plastic waste of both industrial or domestic origin. Therefore, this procedure could be useful in the plastic recycling sector or manufacturers of plastic containers as an initial stage to ensure the quality of the raw material.
The research group is mainly looking for companies interested in acquiring this technology for its commercial exploitation through license agreement. The company should be responsible for the development of the industrial prototype, the validation of the technology, its installation and its introduction into the market. The university will be ready to provide technical assistance in each step, if required.
However, the research group would be also interested in establishing technical cooperation agreements to further develop the laboratory-scale prototype, to find new applications or to adapt it to the company’s needs. The goal of this type of collaboration would be increasing the technology readiness level for a future commercial exploitation of the patent. The university would offer its support based on their know-how; while, the partner sought would provide its expertise to help improve this invention. The university would offer this partner a preferential option to acquire this technology in exclusivity.