Molding materials having stress cracking resistance and based on PMMA/SAN blends

A molding material having stress cracking resistance and containing essentially

• A) from 49 to 99% by weight of a polymer obtainable by polymerizing a C.sub.1 -C.sub.20 -alkyl ester of methacrylic or acrylic acid or a mixture of said esters,
• B) from 0.95 to 50% by weight of a polymer obtainable by polymerizing a monomer mixture comprising
• b.sub.1) from 75 to 82% by weight of a vinyl aromatic monomer and
• b.sub.2) from 18 to 25% by weight of acrylonitrile or methacrylonitrile or a mixture thereof, and
• C) from 0.05 to 1% by weight of a mixture containing
• c.sub.1) a triaryl phosphite of the formula I ##STR19## where R.sup.1 and R.sup.2 are each C.sub.1 -C.sub.12 -alkyl, C.sub.5 -C.sub.8 -cycloalkyl, C.sub.6 -C.sub.10 -aryl or C.sub.6 -C.sub.10 -aryl-C.sub.1 -C.sub.4 -alkyl, where the aryl radicals may be monosubstituted, disubstituted or trisubstituted by C.sub.1 -C.sub.4 -alkyl, and R.sup.3 is hydrogen or C.sub.1 -C.sub.4 -alkyl,
• c.sub.2) an amine of the formula II ##STR20## where n is from 2 to 10, c.sub.3) a benzotriazole of the formula III ##STR21## where R.sup.4, R.sup.5 and R.sup.6 have the meanings of R.sup.1, and optionally
• c.sub.4) a phenol of the formula IV
• AB.sub.k IV
• where k is 1, 2 or 4 and, if k is 1, A is --COOR.sup.7, --CONHR.sup.7 or ##STR22## where R.sup.7 is C.sub.1 -C.sub.21 -alkyl, and, if k is 2, A is --CONH--(CH.sub.2).sub.n --CONH--, ##STR23## where p and m are each an integer of from 1 to 10, and, if k is 4, A is ##STR24## where q is an integer of from 1 to 4, and B is ##STR25## where R.sup.8 and R.sup.9 are each hydrogen, methyl or tert-butyl.