THERMOPLASTIC MOLDING MATERIAL

Rubber-elastic block copolymers of at least one hard block A consisting of styrene monomers and at least one elastomeric block (B/A) of styrene monomers and containing dienes, the glass temperature T g o f block A being over 25 .degree.C and that of block B/A is under 25 .degree.C and the phase volume ratio between block A and block B/A being such that the proportion of the hard phase in the entire block copolymer is 1 to 40 vol %, and the proportion by weight of the diene is und er 50 wt.%. The relative proportion of 1,2 bonds of the polydiene in relation to the sum of 1,2 and 1,4 cis/trans-bonds is under 15 %, process for their production by anionic polymerisation by means of lithium alkyl in a non-polar solvent in the presence of a soluble potassium salt and their use for the production of mouldings.