Formation method null of biaxial stretching compound styrene type resin seat and the said biaxial stretching compound styrene type resin

摘要

PURPOSE:To keep transparency, enhance formability, shorten forming cycle and obtain sheet excellent in trimming properties by a method wherein both core layer made of styrene-based resin layer, which contains the specified amount or more of self- lubricant, and surface layer made of styrene-based resin layer, which contains less than the specified amount and sectional thickness of which lies within the specified range, are integrally and biaxially stretched. CONSTITUTION:The biaxially stretched composite styrene-based resin sheet concerned is made of one layer and surface layers, which are provided on both the sides of the core layer and produced by integrally and biaxially stretching both the core layer made of styrene-based resin layer, which contains 20wt.% or more of self-lubricant, and the surface layers made of styrene-based resin layers, each of which contains less than 20wt.% of self-lubricant and the thickness of each layer lies within the range of 1-20% of the total thickness. If the thickness of the surface layer does not satisfy said lower limit, the surface layers have no effect to suppress the bleeding-out of the self-lubricant in the core layer. If said thickness exceeds the upper limit, the shortening effect of forming cycle becomes small. As the styrene-based resin, which can be used for the core layer and the surface layer, polystyrene having a weight average molecular weight of 200,000-40,000 can be exampled.