METHOD OF PREPARING BUTADIENE-STYRENE BLOCK COPOLYMER

FIELD: copolymerization of butadiene and styrene. SUBSTANCE: polymerization process is carried out in toluene or n-hexane in several stages. In first stage blend comprising 10-20% of butadiene-1,3 is with n-butyl lithium in amount of 10-60 moles per ton of monomers and modifying additive selected from group containing diethylene glycol dimethyl ether, diethylene glycol divinyl ether, diethylene glycol diethyl ether, transmethylated polyamines, methyltetrahydrofurfuryl ether ethyltetrahydrofurfuryl ether, ditetrahydrofurfuryl ether, bis-tetrahydrofurfurylmethoxy based on molar ratio to n-butyl lithium within 0.05 to 0.3. Polymerization process is carried out at 20-60 C to obtain conversion of at least 90%; in second stage divinylbenzene is added based on its molar ratio to n-butyl lithium from 0.1 to 0.5 and maintained for at least 2 minutes; in third stage butadiene is added as blend at the same concentration based on weight ratio to original butadiene within 1-15, modifying additive is added based on increased molar ratio up to 0.5-1.0, and process is carried out at 20-80 C to attain conversion of at least 95%; in fourth stage, styrene is added in amount of 3-15 wt % per total monomers and copolymerization is carried out at the same temperature to obtain conversion of at least 95%. Method makes it possible to prepare rubber predominantly containing 1-2 units in butadiene moiety which has styrene units at two ends of polymer chain with controllable value of elastic restoration and increased physico-mechanical parameters of vulcanizates. EFFECT: more efficient preparation method. 1 tbl