EXPANDABLE STYRENE POLYMER,ITS PRODUCTION,ELASTIC FOAM AND PRODUCTION OF ELASTIC FOAM MOLDING

Expandable styrene polymers (I) for elastic polystyrene (PS) foam contain: (a) 50-90 wt.% PS and/or styrene copolymer contg. at least 50% styrene; (b) 5-30 wt.% styrene-soluble elastomer(s), (c) 5-20 wt.% styrene-contg. block copolymer(s); (d) 1-15 wt.% (w.r.t. a+b+c) low-boiling blowing agent(s), and opt. (e) conventional additives. In the unfoamed bead polymer, component (b) is present in the form of cellular particles and (c) is in the form of particles with a mean size of 0.2-2 microns in the PS phase. Also claimed are: (1) processes for the prodn. of (I) (see below); (2) elastic PS foam with a density of 15-70 g/l, contg. (a), (b), (c) and (e) in amts. as above; and (3) a process for the prodn. of elastic PS foam by heating (I) at a temp. above the softening pt. in a non-gastight mould so as to expand the particles and weld them together. Pref. (b) are styrene-soluble elastomers with a Tg of below 20 degrees C, pref. polybutadiene. (c) are styrene-butadiene (SB) block copolymers with a styrene content of at least 20 wt.%, pref. S-B diblock copolymers or S-B-S triblock copolymers or mixts. thereof.