Catalysts for the polymerization of ethylene oxide

Abstract

THE authors have previously [1] found that the oxides and hydroxides of the alkaline earth metals possess a high catalytic activity for the polymerization of ethylene oxide. In view of the fact that this reaction is one of the few polymerization reactions in which polymers with a molecular weight of 10t-107 are formed on ordinary (non-complex) catalysts, it was of interest to s tudy the rules for the selection of catalysts for this reaction. Recently, information on some new catalysts for this reaction has appeared in scientific [2-4] and patent [5-6] l i terature, but in the majority of published papers [7-10] data are given only on the kinetics of the process on already known polymerization catalysts and no information on the rules for selecting catalysts is given. In the present work, the polymerization of ethylene oxide has been studied by the method of our previous paper [1]. Tubes with a thin internal partition were used for polymerization. The catalyst (0.2-0.5 g) was placed in One part of the tube and was pumped out at a vacuum of 10 -5 mm at a high temperature (the t ime of vacuum conditioning amounted to from 0.5 to 10 hr and the teml~rature from 75 to450 °, depending on the catalysts). After conditioning had been completed, the oven was removed and the tube with the catalyst was sealed off. Ethylene oxide (5 ml) and solvent -benzene -(also 5 ml) were condensed into the other half of the tube. The tube was sealed and was then shaken vigorously, a striker placed in the tube breaking the thin partition. The moment of mixing of the monomer -e thy lene oxide--and the solvent with the catalyst was taken as the start of the reaction. Fur ther polymerization was carried out in a thermostat ted bath fixed in a shaking apparatus (40 oscillations per rain). After the completion of the polymerization, the block polymer ~ catalyst -~solvent were treated with dichloroethane. The catalyst was separated by centrifuging. The polymer was precipitated from the solution by adding n-hexane and was dried at 50-60 °, i.e. somewhat below its melting point. The molecular weights of the polymers were determined as indicated in our previous paper [1]. The surfaces of the catalysts were determined by a weight method from the adsorption of n-heptane or by a volume method