Process for the continuous production of star-block copolymers of a monovinyl aromatic monomer and a conjugated diene

Claim 1

The process for the continuous anionic polymerization of star-block copolymers of a vinyl aromatic monomer and a conjugated diene monomer comprising: (a) producing a polymer having a low weight average molecular weight to number average molecular weight ratio from a vinyl aromatic monomer by continuously feeding a solution of vinyl aromatic monomer in an inert solvent and a hydrocarbyllithium initiator in an inert solvent to form a first mixture in the bottom zone of a first, sealed, cylindrical, pressurized, vertical reactor having a bottom zone, a top zone, and a plurality of intermediate zones, each said zone separated from a adjacent zone by separation plates having a central aperture therethrough, and stirring means carried by a central shaft passing through said apertures with an annular space provided between the shaft and each said separation plate; continuously passing said first mixture from the bottom zone to successive zones through the annular space between the shaft and each said separation plate, said annular space being dimensioned so as to provide a high interstage velocity relative to superficial velocity and a pressure differential of less than one pound per square inch between said successive zones; stirring said first mixture while passing the same through each zone; and continuously removing a solution of a polymer of said vinyl aromatic monomer from the top zone of said first reactor; (b) continuously feeding said solution of polymer and a conjugated diene monomer to form a second mixture in the bottom zone of a second, sealed, cylindrical, pressurized, vertical reactor having a bottom zone, a top zone, and a plurality of intermediate zones, each said zone being separated from an adjacent zone by separation plates having a central aperture therethrough, and stirring means carried by a central shaft passing through said apertures with an annular space provided between the shaft and each said separation plate; continuously passing said second mixture from the bottom zone to successive zones through the annular space between the shaft and each said separation plate, said annular space being dimensioned so as to provide a high interstage velocity relative to superficial velocity and a pressure differential of less than one pound per square inch between said successive zones; stirring said second mixture while passing the same through each zone; and continuously removing a solution of diblock copolymer from the top zone of the second reactor; (c) continuously feeding said solution of diblock copolymer and a polyfunctional coupling agent to a third reactor to produce a star-block copolymer and continuously discharging a solution of the star-block copolymer therefrom; (d) continuously mixing said solution of star-block copolymer with a termination agent in a termination reactor; and (e) separating the resultant star-block copolymer from the inert solvent.