Studio di un processo di riciclo di materiali polistirenici mediante solvolisi

The aim of this work is to investigate a solvolysis process for recycling polystirenic materials either expanded and not, with the target to identify the main design conditions for an industrial plant which provides for successive cycles of dissolution and precipitation to separate the polymer from the flame retardant agent: hexabromocyclododecane (HBCD). In fact the current legislation allows the use of recycled GPPS (General Purpose PolyStyrene) only with a concentration of HBCD less than 100 ppm, because this agent is persistent, bioaccumulative and toxic. The experimental work has been developed through several phases. In the first phase a laboratory set-up was implemented to study the solubilization process of the polymer with dialkylcarbonates or their mixtures and the subsequent precipitation with butanol. In this context, various agitation systems and feeding methods of the mixtures have been experimented to evaluate the influence of fluid dynamics on the process. The following phases were focused on the identification and experimental validation of other solvent / non-solvent couples, keeping the toxicity for humans and the environment as a mandatory parameter. A helpful tool in the search for more efficient solvent / non-solvent pairs in purifying the polymer from HBCD (requiring less cycles of dissolution and subsequent precipitation) was found in HSPiP software, based on Hansen's solubility parameters and allowing to overcome the lack of data in the literature. Then, the experimental set up was implemented and the operating conditions were optimized to obtain the best precipitate and selected the most efficient solvent / non-solvent couple in removing HBCD.