Graft polymers containing phosphorus

A graft polymer comprising:

• a) from 10 to 90% by weight of a crosslinked or partially cross-linked copolymer of from 10 to 60% by weight of a compound corresponding to formula (I) or (II) ##STR4## wherein R represents --H, --CH.sub.3, or --C.sub.2 H.sub.5 ;
• ##STR5## wherein R represents --H, --CH.sub.3, or --C.sub.2 H.sub.5 ;
• and from 90 to 40% by weight of styrene, .alpha.-methyl styrene, acrylonitrile, C.sub.1 -C.sub.8 alkyl acrylate, C.sub.1 -C.sub.8 -alkyl methacrylate, vinyl acetate, or mixtures thereof, as graft basis;
• and
• b) from 90 to 10% by weight of a polymer comprising phosphonic acid derivatives corresponding to formula (III) ##STR6## wherein Y represents --H or --CH.sub.3 ;
• X represents a single bond or --CH.sub.2 ;
• and
• R' represents aryl or alkyl;
• as graft superstrate.