Polyurethane cast elastomers based on poly(butylene oxide) polyols and method for making polyurethane cast elastomers

A hydroxyl-containing copolymer of butylene oxide and ethylene oxide, the copolymer of butylene oxide and ethylene oxide having a hydroxyl equivalent weight of at least 150, an average of 1.8 to 6 hydroxyl groups per molecule of which hydroxyl groups at least 70% are primary hydroxyl groups, and an oxyethylene content of no greater than 10% by weight based on the weight of the copolymer, which copolymer is made by polymerizing butylene oxide and ethylene oxide in the presence of a Lewis acid catalyst having the general formula

• M(R1)1(R2)1(R3)1(R4)0 or 1
• wherein M is boron, aluminum, indium, bismuth or erbium, R1 is a fluoroalkyl-substituted phenyl group and R2 and R3 each are a fluoroalkyl-substituted phenyl group, a fluoro-substituted phenyl group, a chloro-substituted phenyl group or a fluoro- and chloro-substituted phenyl group, provided that R1, R2 and R3 are not all the same, and R4 is a functional group or functional polymer group.