Tailor-made polyols for sustainable polyurethanes by catalyzed copolymerization of CO2 and epoxides

Pohl, Michael; Müller, Thomas Ernst (Thesis advisor); Leitner, Walter (Thesis advisor)

Aachen (2017, 2018)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2017

Abstract

The present thesis discusses aspects concerning the catalyzed synthesis of polyols. Polyols represent fundamental building blocks for polyurethanes beside isocyanates. For the synthesis of polyether polyols from epoxides, double-metal-cyanide (DMC) catalysts are in the focus, which are preferentially used in industrial applications due to their specific characteristics. CO2-based polyethercarbonate polyols (PECs), another category of polyols which can be synthesized by DMC catalyst and from highly interest in actual research topics, are the main focus in my thesis. The thesis is divided into four main chapters. Chapter one gives a general overview on polyurethanes with respect to properties and applications in dependence of the choice of the polyol and isocyanate components. Further, classic and modern synthesis routes for polyols, and the corresponding catalyst system, are described. The ring-opening polymerization of epoxides catalyzed by DMC catalysts is discussed in detail. In the following, chapter two describes the successful minimization of side-products, which are formed during polyol synthesis with DMC catalysts by copolymerization of epoxides and CO2 as well as the separation of the catalyst from the obtained product. By addition of phosphoric acid as additive in the final step of the polyol synthesis, the DMC catalyst is deactivated. Hence, further formation of cyclic carbonates as side-product is prevented. An almost quantitative separation of the DMC catalyst, which after the synthesis remains finely dispersed in the polyol, was achieved by treatment of the polyol with ethanol at elevated temperatures. Chapter three describes different methods for the synthesis of higher functional polyethercarbonate polyols based on DMC catalysis. The incorporation of functional, cyclic latent AxBy-type monomers into the polymer chain increases the average functionality of the polyol and allows controlling the polymer architecture. Developing methods to raise the sustainability of the polyols is another focus point. In this context, the successful synthesis of polyethercarbonate polyols based on sugar alcohols and citric acid as chain transfer reagent is described. Finally, in chapter four the polymer dynamics of classical polyether polyols and modern polyethercarbonate polyols is described. New application areas of polyethercarbonate polyols are discussed based on their distinct visco-elastic properties at relative low molecular weights.