trioxide 0 0022 parts were charged to a 4 necked flask with a scaled bottom runoff tube and fitted with a stirrer internal thermometer nitrogen inlet and a condenser set for distillation the flask was heated in an electric mantle through which the bottom runoff tube protruded the temperature of the contents of the flask was raised to 260 degrees plus minus 5 degrees c over half an hour and held at 260 degrees c plus minus c for three hours additionally products containing both eo and po can be made by substituting an ethylene oxide propylene oxide polymer of the same molecular weight for the polyoxyethylene material above spinning grade poly ethylene terephthalate 134 4 parts a block polymer 2 1 ethylene oxide to propylene oxide having a molecular weight of 1540 mwu 308 parts and antimony trioxide 0 0022 part were charged to a 4 necked flask with a scaled bottom runoff tube and fitted with a stirrer internal thermometer nitrogen inlet and a condenser set for distillation the flask was heated in an electric mantle through which the bottom runoff tube protruded the temperature of the contents of the flask was raised to 260 degrees plus minus 5 degrees c over half an hour and held at 260 degrees c plus minus 5 c into a suitable reaction flask equipped with a thermometer nitrogen sparge and agitator is added the specified amount of raw material polymer selected from examples 1 3 the raw material polymer is.