| 摘要 |
UV-stabilised, multilayer polycarbonate sheet (I) contains 1.1 a base sheet made of thermoplastic polycarbonate (PC) contg. no UV absorber or from 0 to 1 wt.% UV absorber, with a viscosity of 500-2500 Pa.s at 280 deg.C and a shear rate of 100 s<-1> and, on at least one side, 1.2 an outer layer of thermoplastic PC contg. 2-20 wt.% UV absorber (II), with a viscosity (under the above conditions) of 200-2300 Pa.s, which is at least 50 Pa.s lower than the viscosity of 1.1. Also claimed is a process for the prodn. of (I) by co-extrusion, by combining the melts for the core material and the outer layer(s) with the aid of a coextrusion adaptor and extruding the combination into the required form in a closed die. |
