Aromatic vinyl polymer resin composition and its molding

Abstract

Provided are an aromatic vinyl polymer resin composition capable of being molded into resin foam sheets having good surface smoothness and glossiness well balanced with the mechanical strength thereof even when the expansion ratio in molding is increased, and resin foam sheets and containers of the composition. The resin composition comprises (A) from 80 to 98% by mass of an aromatic vinyl polymer resin having a weight-average molecular weight measured through GPC of from 200,000 to 400,000, a ratio of weight-average molecular weight to number-average molecular weight ranging from 2.2 to 3.6, a number of branches of from 0.1 to 1.0 in one molecule having an absolute molecular weight of 1,190,000 measured through GPC-MALLS, and a melt flow rate of from 1.5 to 3.5 g/10 min, and (B) from 2 to 20% by mass of a styrene-diene block copolymer or its hydrogenate. This is molded into a resin foam sheet through extrusion foaming, and the sheet is thermoformed into containers.

1 - 5 . (canceled)  
     
     
         6 . A resin foam sheet formed by molding the aromatic vinyl polymer resin composition comprising (A) from 80 to 98% by mass of an aromatic vinyl polymer resin having (1) a weight-average molecular weight (MwL) measured through GPC of from 200,000 to 400,000, (2) a ratio of weight-average molecular weight (MwL) to number-average molecular weight (MnL), (MwL)/(MnL) ranging from 2.2 to 3.6, (3) a number of branches of from 0.1 to 1.0 in one molecule having an absolute molecular weight of 1,190,000 measured through GPC-MALLS, and (4) a melt flow rate of from 1.5 to 3.5 g/10 min, and (B) from 2 to 20% by mass of a styrene-diene block copolymer or its hydrogenate, 
 through extrusion foaming to an expansion ratio of from 3 to 12 times.    
     
     
         7 . The resin foam sheet of  claim 6 , wherein the aromatic vinyl polymer resin (A) is a polystyrene resin.  
     
     
         8 . The resin foam sheet of  claim 6 , wherein the styrene-diene block copolymer or hydrogenated (B) is styrene-butadiene block copolymer or styrene-isoprene block copolymer or hydrogenate thereof that contains polystyrene block structure units to an extent of from 10 to 90% by mass thereof.  
     
     
         9 . A container molded by thermoforming the resin foam sheet by molding an aromatic vinyl polymer resin composition comprising (A) from 80 to 98% by mass of an aromatic vinyl polymer resin having (1) a weight-average molecular weight (MwL) measured through GPC of from 200,000 to 400,000, (2) a ratio of weight-average molecular weight (MwL) to number-average molecular weight (MnL), (MwL)/(MnL) ranging from 2.2 to 3.6, (3) a number of branches of from 0.1 to 1.0 in one molecule having an absolute molecular weight of 1,190,000 measured through GPC-MALLS, and (4) a melt flow rate of from 1.5 to 3.5 g/10 min, and (B) from 2 to 20% by mass of a styrene-diene block copolymer or its hydrogenate, 
 through extrusion foaming to an expansion ratio of from 3 to 12 times.    
     
     
         10 . The container of  claim 9 , wherein the aromatic vinyl polymer resin (A) is a polystyrene resin.  
     
     
         11 . The container of  claim 9 , wherein the styrene-diene block copolymer or hydrogenated (B) is styrene-butadiene block copolymer or styrene-isoprene block copolymer or hydrogenate thereof that contains polystyrene block structure units to an extent of from 10 to 90% by mass thereof.