PETpla.net Insider 12 / 2012

MATERIAL / RECYCLING 20 PET planet insider Vol. 13 No. 12/12 www.petpla.net M-PET recycling technology From waste to primary PET The Czech company PTP-Plastic Technologies & Products s.r.o.operates a reference plant for the production of M-PET in Jίlové u Prahy. Large-scale technical maturity was achieved with the extrusion system with conical parallel twin screws as central components developed by the Upper Austrian MAS-Maschinen- und Anlagenbau Schulz GmbH. M-PET process The M-PET process is a patent application from 2002 which describes a recycling process for PET bottles, of which the end product is equiva- lent to primary PET, even better in some respects but without having to use an SSP (Solid State Polymeriza- tion) process. The M-PET produced in this way represents a high quality alternative to the original material. The modification process is based on the research work conducted over 30 years ago by the Georgian chemists George Javakhishvili and Levan Dadi- ani and their Russian colleague Viktor Bulgakov in the university institutes of the former Soviet Union. Research centred on the interactions between different polymer molecules in contact with polyesters. The focus was placed on polysiloxanes (silicone-oxygen polymers), silazanes (silicone-nitro- gen polymers) and silanes (silicone- hydrogen polymers). One result of this research work was the discovery that silane compounds, preferably poly- hydrosiloxane in combination with a plasticiser such as di-octylphthalate, di-nonylphthalate or di-butylsebacate can enter into compounds with poly- ester molecules. The combination of the active sub- stances acts as a polymer adhesive. In this way the short-chain molecules, as they arise in decomposition prod- ucts through all kind of processes, are recombined to or even beyond the starting chain lengths. In addition to chain extensions, the modification agent also promotes the creation of cross-linking which counteracts the characteristic tendency of PET to crystallise. In order to achieve these effects, the addition of only 4 to 5% by weight of the modification agent is sufficient. The recyclate thus manu- factured is referred to as M-PET. It differs from the conventionally treated recycled PET primarily in terms of the higher resistance to oxidation and hydrolysis, higher elasticity and tensile strength as well as higher thermal dimensional resistance. The gas permeability which is decisive for use in the production of drinks bottles achieves the level of new PET goods. The production process to modify the starting material is very simple. While originally, i.e. in 2002 at the time of the patent application, the modification agent had to be added to the PET flakes in a reactor mixer and had to be agitated at around 130 °C for between 50 and 100min so as to finely distribute and gel the flakes, the modificator can be added in liquid form or alternatively as granulate directly in the MAS extruder. From laboratory to industrial production During the time between patent application and granting of patent in 2006 (identification number DE 60208241T2 24.08.206) several test certificates and approvals for food packaging relevant to the interna- tional application were obtained and a reference plant for industrial produc- tion was being set up. The first one is within the responsibility of PTP-Plastic Technologies & Products B.V. in Amsterdam, the headquarterse of the cooperate holding company. Parallel to this, a reference plant was estab- lished at the Czech location of Jίlové u Prahy. There, the process technol- ogy was transferred from a laboratory scale to industrial volumes and optim- szed in several evolutionary stages. Entry to production on an industrial scale was made with plant technol- ogy surrounding a 75mm twin screw extruder with co-rotating parallel The Mas extruder has a modular design and is avail- able in six sizes for dis- charge performances from 200 to 1,800kg/h.