Molding materials containing styrene/acrylonitrile copolymers and ethylene oxide/propylene oxide three-block copolymers

A molding material which contains

• A. styrene/acrylonitrile copolymers and
• B. three-block copolymers X-Y-X, which copolymers contain
• b.sub.1. a central block Y which substantially consists of propylene oxide units and has a number-average mean molecular weight of up to 3,000, and
• b.sub.2. at each of the two ends, at least one block X, consisting substantially of ethylene oxide units, the proportion of b.sub.2, based on three-block copolymer, being less than 85% by weight, with or without
• C. effective amounts of other, conventional additives, wherein the styrene/acrylonitrile copolymers A substantially consist of
• (a.sub.1) from 20 to 35% by weight of acrylonitrile units and
• (a.sub.2) from 80 to 65% by weight of styrene units and/or .alpha.-methylstyrene units, or a mixture of the said units, component B is present in an amount of from 0.1 to 2% by weight, based on the sum of A and B, and the proportions of b.sub.1 and b.sub.2, based on the three-block copolymer X-Y-X, are
• (b.sub.1) from 80 to 95% by weight and
• (B.sub.2) from 5 to 20% by weight,
• whilst the number-average mean molecular weight of (b.sub.1) is greater than 700 and the number-average mean molecular weight of the sum of the X blocks (b.sub.2) is from 140 to 1,000.