A polymer comprising: a) a thermosetting epoxy-terminated oxazolidinone ring containing polymer modified by b) core shell rubber particles, wherein at least 50% of the core shell rubber particles are prepared by a process comprising: I) carrying out an emulsion polymerization of monomers in an aqueous dispersion medium to form thermoplastic core shell rubber particles; II) coagulating the thermoplastic core shell rubber particles to form a slurry; and III) dewatering the slurry to form dewatered particles and IV) drying the dewatered particles to form dried particles is disclosed.