| abstract |
Polyurethane polyether-based elastomers are described which are thermoplastic, recyclable and have increased high temperature resistance which permits fabrication by injection molding. The elastomers are the product of reaction of 4,4'-methylenebis(phenyl isocyanate), a particular group of polypropylene oxide-polyethylene oxide block copolymers and an extender [straight chain aliphatic diols C2-6 or the bis(2-hydroxyethyl ether) of hydroquinone or resorcinol]. The block copolymers have at least 50 percent primary hydroxyl groups, a pH in the range of 4.5 to 9, a content of alkali metal ion less than 25 ppm and a molecular weight of 1000 to 3000. The minimum ethylene oxide (E.O.) residue content (percent by weight) of the polyether for any molecular weight (M.W.) is governed by the equation: <IMAGE> In a particularly preferred embodiment the elastomers are prepared by replacing up to 25 percent by equivalents of the extender by certain diols (polyethylene glycols up to 1500 M.W. preferred). |