Basics Plastics made
Basics Plastics made from CO 2 Carbon dioxide as chemical feedstock In the last decades much work has been done in the field of carbon dioxide capture, purification, and transformation into useful and new fuels, chemicals and polymers. The explosion of interest in CO 2 has led to a new awareness at industrial, societal, and scientific levels with the result that carbon dioxide is no longer a mere waste product, but rather an abundant, low cost raw material. Moreover, using carbon dioxide as chemical feedstock plays a key role for the sustainable future of chemical industry and opens up new prospects for solving global challenges, and in the end it could help boosting a low carbon society. High on the European research agenda, scientists and engineers around the world are very active in Carbon Capture Utilization (CCU) research, especially in the fields of solar fuels (power-to-fuel, power-to-gas), but also in CO 2 -based chemicals and polymers. Meanwhile the implementation is only a stone’s throw away. First pilot and commercial production plants are already installed in which CO 2 is used either directly as polymer building block or indirectly in combination with other monomers that are not CO 2 - derived to obtain a large array of final plastics with tailormade properties. This paper is mainly focused on polypropylene carbonate (PPC), polyethylene carbonate (PEC) and polyurethanes (PUR) based on CO 2 (figure 1). Polypropylene carbonates (PPC) and Polyethylene carbonates (PEC) Polypropylene carbonates (PPC) are biodegradable aliphatic polyesters and the first remarkable example of Figure 1: Routes to PPC, PEC and PU from CO 2 (nova-Institut GmbH, 2012) plastic that is synthesized from copolymerization of CO 2 and propylene oxide (C 3 H 6 O). PPC contains up to 50 % CO 2 by mass, shows good biodegradability properties, high temperature stability, high elasticity and transparency, and has a memory effect. These characteristics open up a wide range of applications, including countless uses as packaging films and foams, dispersions and softeners for brittle plastics. Other big advantages of PPC are its thermoplastic behaviour, which is similar to many existing plastics, the possible combination with other polymers, and its use as filler. Moreover, PPC does not require special tailor-made machines to process it, making PPC a ready-to-use alternative to many existing plastics. PPC is also a good softener for biobased plastics. Many of these, for example PLA and PHA, are originally too brittle and can therefore be used for many applications only in combination with additives. Of course, it is not new, but it clearly illustrates the comprehensive application possibilities of this CO 2 -based polymer: PPC gives new options and offers an extensive range of material characteristics in combination with PLA or PHA. This keeps the material biodegradable and translucent, and it can be processed without any trouble in existing machinery. In Germany some years ago, BASF, Siemens and the TU Munich worked on PPC and combined it with PHA and PLA for vacuum cleaner and refrigerator parts to demonstrate the new material’s potential and properties. Besides Novomer and Empower Materials in the USA, the Norwegian company Norner and South Korea’s SK Innovation are also well-known companies who are PPC PO CO 2 Polyol PEC EO Isocyanate PUR 46 bioplastics MAGAZINE [06/15] Vol. 10
Basics By: Barbara Dommermuth and Achim Raschka nova-Institute Hürth, Germany working on PPC. Novomer, an emerging sustainable chemistry company, was founded in 2004 and is focused on commercializing high performance, cost-effective, environmentally responsible polymers and chemicals based on proprietary catalyst technology (figure 2). This novel technology allows traditional chemical feedstock such as propylene oxide with carbon dioxide or carbon monoxide from pollution to be converted into cost-effective sustainable materials for a wide variety of applications from thermoplastics to coatings. This results in a family of novel PPC polymers that contain up to 50 % CO 2 by weight and they are thus alternative to conventional fossil-based polyether, polyester and polycarbonate polyols currently on the market with up to 90 % lower CO 2eq -emissions. Novomer’s proprietary cobalt-based catalyst system is cost-effective (20 to 40 % lower cost) and produces a polymer with an extremely precise backbone, and little to no by-products. In addition, the polymerization reaction occurs at slightly above ambient temperature so the entire process generates a very small carbon footprint. The recent commercial interest necessitated an increased volume, so the process has been scaled up to produce PPC in the multi-thousand-tonne range. Novomer started the first commercial production of PPC in 2014 with a production capacity of 5,000 t/a at Albemarle, Houston, Texas. They are using CO 2 from ethanol fermentation, ammonia, hydrogen and ethylene oxide production, reformers, natural gas wells and the flue gas from coalfire power plants and replace up to half of the fossil fuel in the materials. End of 2014 the company announced that Jowat AG, a leading German supplier of industrial adhesives, is the first to commercially adopt Novomer’s new Converge PPC polyols. Jowat is using the polyols in polyurethane hot melt adhesive applications. Novomer has also a proprietary technology to obtain polyethylene carbonate (PEC )from ethylene oxide and CO 2 by a process similar to the one used for the production of PPC. PEC is 50 % CO 2 by weight and can be used in a number of applications to replace and improve traditional petroleum-based plastics currently on the market. PEC exhibits excellent oxygen barrier properties that make it useful as a barrier layer for food packaging applications. Furthermore, PEC has a significantly improved environmental footprint compared to polymers typically used as barrier layer such as ethylene vinyl alcohol (EVOH) and polyvinylidene chloride (PVDC). Alongside SK Innovation, further companies from Asia are working in the PPC area such as Jiangsu Jinlong- CAS Chemical Co., Ltd. with a PPC production capacity of 22,000 t/a. Inner Mongolia Mengxi High-Tech Group Co., Ltd. has also been producing PPC commercially with a production capacity line of 3,000 t/a since 2004. They plan to further expand in the coming years. Both companies are from China. Econic Technologies is a highly innovative, and fast growing chemical technology company, based at Imperial College, London. The company has developed a homogeneous bimetallic complex for the manufacturing of polymers via co-polymerisation of carbon dioxide and Figure 2: Novomer’s CO 2 -based polyols platform (Novomer 2014) Propylene oxide (PO) CO 2 Novomer catalyst Polypropylene carbonate (PPC) 43 wt% CO O 2 O O Low Mw polyols (thermosets) High Mw thermoplastic polymers PO + CO 2 + Catalyst + Initiator PO + CO 2 + Catalyst HO I OH OH I HO • Initiator spurs polymerizations • No initiator present during reaction • Creates more, shorter PPC chains • Creates fewer, longer PPC chains bioplastics MAGAZINE [06/15] Vol. 10 47
