Published May 1998
This Review updates information on the major commercial processes currently used to produce rubber elastomers—styrene-butadiene rubber (SBR) and polybutadiene rubber (BR). The Review does not address processes for styrene-butadiene block copolymers, given that these copolymers are basically resins rather than elastomers. [PEP Report 207, Specialty Styrenic Thermoplastics (October 1991), evaluated styrenic block copolymers, and PEP Report 104, Thermoplastic Elastomers (November 1976), evaluated styrene-butadiene thermoplastic elastomers.]
SBR elastomer is principally manufactured by the emulsion-polymerization process or by the solution-polymerization process. Although the emulsion process is dominant worldwide, SBR producers are moving toward the solution technology because it yields an elastomer of superior properties. In the emulsion processes, a major portion of the SBR elastomer is manufactured via the cold-emulsion polymerization method; globally, cold emulsion accounts for more than 90% of emulsion SBR.
The major commercial process for producing BR is solution polymerization. Producing BR via the emulsion process is relatively insignificant and is not evaluated here. Cobalt- and lithium-based catalysts account for a major portion of global BR production.
Basic manufacturing methods for SBR and BR have not radically changed since the early 1970s, when PEP Report 64, Styrene-Butadiene Elastomers (November 1970), and PEP Report 73, Polybutadiene (1970), were issued. Better recipes, however, have been formulated and implemented since then, producing diverse rubbers of a much superior quality.
In this Review we evaluate SBR and BR emulsion and solution processes that account for a major portion of the SBR and BR consumed globally. We both update the referenced reports and use recent recipes and formulations claimed in the patents as design bases for our evaluation. We highlight radical changes that have taken place in the process flowsheet or in the basic recipe.
We base the evaluation of the processes on a production capacity of 77.5 million lb/yr (35,000 t/yr) of SBR and 100 million lb/yr (45,000 t/yr) of BR, respectively, at a 0.9 stream factor. The capacities selected represent typical world-scale commercial units. We assume that the production units are located in the U.S. Gulf Coast region