A process for the preparation of expandable styrene polymers having a molecular weight Mw of greater than 170,000 g/mol, which comprises conveying a blowing agent-containing styrene polymer melt having a temperature of at least 120° C. through a die plate with holes whose diameter at the die exit is at most 1.5 mm, and subsequently granulating the extrudate, and expandable styrene polymers (EPS) having a molecular weight Mw of more than 170,000 g/mol with 0.05 to 1.5% by weight of internal water.