RUBBER-MODIFIED STYRENE POLYMER RESIN COMPOSITION FOR EXTRUSION FOAMING, EXTRUSION-FOAMED SHEET OF THE RESIN AND PRODUCTION OF EXTRUSION-FOAMED SHEET OF THE RESIN

摘要

PURPOSE: To easily obtain an extrusion-foamed sheet having sufficiently developed foam membrane, high closed cell ratio and excellent foaming agent retaining performance and, accordingly, excellent post-forming performance. CONSTITUTION: This rubber-modified styrene polymer resin composition for extrusion-foaming contains a resin composed of (A) a rubber-modified styrene polymer having a methanol-soluble content of <=4wt.% and containing rubber polymer particles having an average particle diameter of <=3μm and dispersed in the continuous phase of a styrene polymer having a Z-average molecular weight of >=330,000 and (B) a styrene polymer having a Z-average molecular weight of >=700,000. The extrusion-foamed sheet is produced by extrusion- foaming the resin composition incorporated with a volatile foaming agent. The resin component may be compounded with 5-25wt.% (based on the total resin component) of a styrene-butadiene block copolymer or its hydrogenated product.