STUDIES ON THE THERMOOXIDATION OF ETHERS AND POLYETHERS .4. INHIBITION OF THE HIGH-TEMPERATURE OXIDATION OF POLYETHER ALCOHOLS BY TRIVALENT PHOSPHORUS-COMPOUNDS

The causes of high antioxidant efficiencies of aromatic phosphites and phosphonites in the high temperature stabilization of a commercial polyether alcohol were established using kinetic methods. The oxidation of the aliphatic polyether as well as the transformation of the organo-phosphorous stabilizers are described. The trivalent phosphorus compounds are initially oxidized at a high rate followed by a decomposition of the P(V)-compound, by hydrolysis and/or substitution, to the phosphoric acid. The phenols, acting as radical chain breakers, released in this process, plus the hydroperoxide decomposing effect of the P(III)-compounds, cause their high antioxidant activity. The analytical results (P-31-NMR spectroscopy, HPLC) were completed by oxygen uptake measurements, carbonyl indices and by investigations of the hydrolysis and thermostability of the phosph(on)ites.