FIELD: polymer production. SUBSTANCE: process is conducted in reaction apparatus having two interconnected reaction zones. Polyolefin particles and at least one monomer polymerizing in presence of free radicals are fed into reaction zones maintaining free-radical polymerization and essentially unoxidized medium conditions and then discharging graft copolymer product. Polymer particles pass the first reaction zone under fast fluidization conditions, enter the second reaction zone wherein they move in piston flow by gravity and are then returned into the first reaction zone, and so on. EFFECT: simplified process, reduced deposits, improved ingredients' mixing, and increased heat exchange surface. 19 cl, 2 dwg, 1 tbl, 8 ex
