STAR POLYMER, METHOD OF PREPARATION THEREOF, AND LUBRICATING OIL COMPOSITION Russian patent published in 2000 - IPC

FIELD: polymer production. SUBSTANCE: invention provides new star polymer applicable as viscosity index-improving additive and distinguishing by including at least partially hydrogenated polyisoprene blocks and at least partially hydrogenated polybutadiene blocks assembled into molecules with structure (EP-EB-EP′)_n-X, where EP is outside polyisoprene block with number-average molecular weight (MW1) 6500 to 85000 before hydrogenation; EB polybutadiene block with number- average molecular weight (MW2) 1500 to 15000 before hydrogenation and having at least 85% monomer units attached in position 1,4; EP' inside polyisoprene block with number-average molecular weight (MW3) 1500 to 55000 before hydrogenation; star polymer containing less than 15% of butadiene units and MW1/MW3 ratio ranging from 0.75:1 to 7.5: 1; X is nucleus of polyalkenyl coupling agent; and n number of block- polymer deviations in star-shaped polymer in case of coupling of at least 2 mole of polyalkenyl coupling agent per 1 mole of living block-polymer molecule. EFFECT: improved viscosity-modifying characteristics of polymer. 13 cl, 4 tbl