Catalytic polymerization of propylene oxide

Abstract

Polyoxypropylene with a molecular weight of one to several thousand is one of the key starting components in the production of polyurethane foams, coatings and adhesives. In industry, polyoxypropylene is traditionally produced by polymerization of propylene oxide (PO) using potassium or sodium hydroxides and low molecular weight hydroxyl initiators, such as glycerol and propylene glycol. The significant number of side processes is the main disadvantage of using alkaline catalysts, which leads to a decrease in the molecular weight of polyoxypropylene. Modern double metal cyanide (DMC) catalysts allow the production of polyols with much higher molecular weights and much lower polydispersity, but they are easily deactivated in the presence of low molecular weight hetero-organic compounds. This paper presents the results of research related to the polymerization process of propylene oxide in the presence of potassium glycerate and subsequent polymerization of PO using the resulting oligomers and DMC catalyst (Arcol® Catalyst 3). The synthesized polyols were analysed by gel permeation chromatography and 13C NMR spectroscopy. For successful initiation of the polymerization process, the optimal molar ratio of the first portion of OP to glycerol initiator is approximately 3:1, and the optimal feed rate of OP per 1 mol of initiator is about 1.5 mol OP per hour. A procedure for obtaining propylene oxide oligomers using potassium glycerate with a given molecular weight in the range Mn = 500-1300 was developed. The synthesis of polyols with Mn > 3000 was carried out using the effective zinc hexacyanocobaltate DMC catalyst Arcol® Catalyst 3. According to 13C NMR spectra of polyols, the two terminal OH groups of glycerol form two polymer chains, the middle OH group of the secondary carbon atom of glycerol does not participate in polymerization.