| 摘要 |
PURPOSE:To obtain polycarbonate resin foam having high hardness and strength skin layer even when the expansion ratio of the foam is raised to some degree by a method wherein specified relationships are established between the weight average molecular weights of polycarbonate resins, which respectively form front layer and rear layer and between their layer thickness. CONSTITUTION:The average molecular weight of front layer is made 1.5 times or more as heavy as that of rear layer, in the case of two layers, or of core layer, in the case of three layers or more. Concretely, a formula I holds between the weight average molecular weight MWA of polycarbonate resin consisting of the front layer and that MWB of polycarbonate resin consisting of the other layer. Further, a formula II holds between the thickness LA of the polycarbonate resin layer of the front layer (or the sum of the thickness of the outermost layers in the case of three layers or more) and the thickness LB of that of the resin layer (or the thickness of an intermediate layer). Thus, even when the density of foam is made lower, the scratch resistance of the surface of the foam can be raised. |
