| 摘要 |
PURPOSE:To provide the titled material having extremely small spring constant and excellent vibration-damping property, useful for the vibration-damping of railroad, etc., and composed of a foamed polyurethane elastomer having low degree of expansion and having a structure characterized by the density varying from the intermediate layer toward the surface layer, and having dense layers near the surface. CONSTITUTION:The objective material is composed of a foamed polyurethane elastomer having low degree of expansion, and having three-layered structure consisting of a dense layer 8, a porous layer 7 and a dense layer 8, i.e. having dense layers at the surface region, wherein the density varies continuously or discontinuously from the intermediate layer toward the surface layers. The foam can be produced by reacting (A) an organic polyisocyanate with (B) a polyether polyol having an average number of functional groups of 2.5-3.5 and a number-average molecular weight of 4,500-8,500, and (C) a chain extender at a ratio to give an NCO index of 90-110, in the presence of (D) freon gas having a boiling point of 40-70 deg.C as a foaming agent. |
