. . "Polyalkylene glycols are obtained from monomers such as ethylene oxide, propylene oxide, butylene oxide or tetrahydrofuran by polymerization in the presence of boron trifluoride or by polyaddition with initiator compoundshaving reactive hydrogen atoms, such as water, alcohols, amines or bisphenol A. Mixtures of the monomers may also be used simultaneously or in succession." . .