Patent ID: 6372863
Filing Date: 2002-04-16
Classification: B60C,C08F

Abstract:
A process of synthesizing random styrene-butadiene rubber having a low level of branching and a low vinyl content which comprises: (1) continuously charging 1,3-butadiene, styrene, an organolithium initiator, and an organic solvent into a first polymerization zone, (2) allowing the 1,3-butadiene and styrene to copolymerize in the first polymerization zone to total conversion which is within the range of about 60 percent to about 90 percent to produce a polymer cement containing living styrene-butadiene chains, (3) continuously charging the polymer cement containing living styrene-butadiene chains and additional 1,3-butadiene monomer into a second polymerization zone, wherein from 20 percent to 40 percent of the total amount of 1,3-butadiene changed is charged into the second polymerization zone, (4) allowing the copolymerization to continue in the second polymerization zone to a conversion of the 1,3-butadiene monomer of at least 90 percent, wherein the total conversion of styrene and 1,3-butadiene in the second polymerization zone is limited to a maximum of 95 percent, (5) withdrawing a polymer cement of random styrene-butadiene rubber having living chain ends from the second reaction zone, (6) killing the living chain ends on the random styrene-butadiene rubber, and (7) recovering the random styrene-butadiene rubber from the polymer cement, wherein the copolymerizations in the first polymerization zone and the second polymerization zone are carried out at a temperature which is within the range of about 70Â° C. to about 100Â° C., and wherein the amount of styrene charged into the first polymerization zone is at least 5 percent more than the total amount of styrene bound into the random styrene-butadiene rubber.