Patent ID: 6242536
Filing Date: 2001-06-05
Classification: C08F

Abstract:
A process for preparing block copolymers predominantly of a structure S-B-S with at least one polybutadiene terminal block, wherein S represents a block of polystyrene and B represents a block of polybutadiene, the process comprising the steps of:(a) reacting a hydrocarbyl lithium having up to 10 carbon atoms with an appropriate amount of butadiene to form a block of polybutadiene representing 2-12 parts by weight per 100 parts by weight of the first block polystyrene to which this initial block polybutadiene will be attached and thereby produce a polybutadiene*-Li precursor;(b) adding styrene to the polybutadiene*-Li precursor of step (a) and effecting polymerization of said styrene with said polybutadiene*-Li precursor in a solvent of 15 to 60% by weight cyclohexane and 40 to 85% by weight alkane to give a polybutadiene*-polystyrene-Li product;(c) thereafter adding butadiene in an alkane diluent to the polybutadiene*-polystyrene-Li product of step (b) and effecting polymerization of said butadiene with said polybutadiene*-polystyrene-Li product to give a polybutadiene*-polystyrene-polybutadiene-Li product while dispersed in a 0-10% cyclohexane and 90-100% alkane solvent; and(d) thereafter effecting the addition of a second polystyrene block onto said polybutadiene*-polystyrene-polybutadiene-Li product.