Polyamide thermoplastic composition with improved impact strength properties

The invention relates to a polyamide-based thermoplastic composition comprising, by weight: 50 to 98 parts of a polyamide (A1) nondiamine; 0.2 to 40 parts, preferably 0.2 to 9 parts, of a polyamide (A2) diamine, said polyamide (A2) being different from the polyamide (A1) and the ratio by mass (A2)/(A1) being less than 1; 1 to 60 parts, preferably 1 to 30 parts, of a reactive impact modifier (B) or of a blend of modifiers comprising at least one reactive impact modifier (B) or of a blend (B') comprising at least one impact modifier and at least one reactive modifier. It also relates to an impact modifier composition and to the process for the preparation of a thermoplastic composition according to the invention using such an impact modifier composition.