It's an Ideas Thing: Polymer Plant Engineers Think Bigger

Traditionally, polycarbonates are produced by a reaction of bisphenol A and phosgen — approximately one billion kilograms of polycarbonate are produced with this method each year. Phosgene, howerver, is a highly toxic compound, which was used as a chemical weapon in Worldwar One, where it caused more than 85 000 deaths. No wonder, that EPC promotoes a production method that does not need this dangerous gas.

EPC’s 2nd generation Melt Polycarbonate Process (also known as a phosgene-free process) is based on the direct melt polycondensation of the monomers Bisphenol-A (BPA) (solid or liquid supply) and Diphenyl carbonate (DPC) to produce polycarbonate chips. This is not only much safer for workers and the environment, but also eliminiates the need for the extradordinary safety measures that come with phosgene handling. The main process steps in EPCs 2nd generation PC process are:

• Raw material preparation

• Transesterification

• Polycondensation

• Additives Extruder System

• Pelletizing

The raw materials are undergo melting and mixing as well as sophisticated purification steps. After the raw material preparation, a catalyst is introduced and the raw materials are converted in the transesterification step. In order to achieve the required conversion rate, the material is continuously passed through a number of transesterification reactors which are aligned in series to enhance the process controllability and to increase the raw material efficiency.

The next step is the polycondensation, during which the intermediate product is further reacted to produce long polymer chains with the desired length. In this step EPC's patented horizontal disc ring reactors are used to create a high surface area and to assist mass transfer during the polycondensation. The polymer melt having the desired final chain length is fed from the last reactor towards a high performance additives extruder system in which specific additives are incorporated into the polymer melt. The phenol that is split-off as a by-product during the reaction can be purified for further use in the raw material production. By re-using the leftovers and byproducts in the production process, the process' sewage water does not get contaminated and can be treated in regular waste water plants.