FIELD: polymers. SUBSTANCE: invention relates to preparing polypropylene grafted copolymers with anhydride groups. Invention describes method for preparing grafted copolymers containing anhydride groups that involves the following steps: (1) preparing the grafted copolymer containing the main chain of material of propylene polymer with grafted polymerized monomers taken among the group consisting of: (a) at least one C1-3-alkyl-substituted acrylic acid and (b) mixture of (a) with at least one vinyl monomer that is able to copolymerization where the total amount polymerized monomers is about 20-240 parts per 100 parts of material of propylene polymer and amount of substituted acrylic acid is equal or above 60 mole% of polymerized monomers; and (2) heating the prepared grafted copolymer to temperature about 170-300 C for dehydration of acid groups in grafted copolymer to form anhydride groups; and grafted copolymer also. Grafted copolymer of this invention shows good value of the strength balance (rupture elongation), impact viscosity and strength of welded seams in the end product and their impact viscosity can be modified easily with broad order of rubber materials. EFFECT: improved preparing method, valuable properties of copolymers. 11 cl, 6 tbl, 4 dwg, 5 ex
