Means to control particle size and eliminate fouling in the synthesis of

Abstract

Syndiotactic 1,2-polybutadiene is a thermoplastic resin which has double bonds attached in an alternating fashion to its polymeric backbone. Films, fibers and molded articles can be made utilizing syndiotactic 1,2-polybutadiene. It can also be blended into rubbers and cocured therewith. It is generally preferred to synthesize syndiotactic 1,2-polybutadiene in an aqueous medium by suspension or emulsion polymerization. In such aqueous polymerization techniques reactor fouling and particle size control problems are frequently encountered. This invention is based upon the unexpected finding that reactor fouling can be greatly reduced or eliminated and that particle size can be regulated by conducting such aqueous polymerizations in the presence of a controlled amount of dissolved oxygen which is within the range of about 0.01 ppm to about 4 ppm. This invention more specifically discloses a process for preparing syndiotactic 1,2-polybutadiene in an aqueous medium with minimal reactor fouling which comprises polymerizing 1,3-butadiene monomer in the aqueous medium in the presence of (1) a catalyst system which is comprised of (a) transition metal compound, (b) an organoaluminum compound and (c) at least one member selected from the group consisting of carbon disulfide, phenyl isothiocyanate and xanthic acid and (2) from about 0.01 ppm to about 4 ppm of oxygen.