Styrene Butadiene Elastomers

Styrene-butadiene rubber, abbreviated SBR* (also called GR-S rubber), has been the most important synthetic rubber. It was first made by an emulsion process at 122'F (hot process). Later a cold emulsion process at 41�F was developed and it is now the main process for making SBR. In recent years solution processes have evolved and those now in commercial practice use an alkyllithium catalyst. The alfin (named from alcohol and olefin) process, which is a solution process using a special catalyst, has also been developed and is now being commercialized.

This report evaluates emulsion processes for manufacture of solid elastomer, for making high solids latex, and for making low solids latex; the solution process for making a random copolymer using alkyllithium as a catalyst; and the alfin process. In each case, a basic version of the process is evaluated in detail, and any important process variations on the basic version are covered in the discussion. Block copolymers and hydrogenated copolymers are also discussed. Oil extension and black masterbatching are included but no other means of blending are considered.

Not included in the report are copolymers containing more than 50% styrene. While the manufacturing processes for the high-styrene copolymer closely resemble the ordinary SBR manufacturing process, these copolymers are resins, not elastomers. Also generally not considered as SBR are those copolymers with a third monomer component, except a few grades with a minor amount of a third component, namely, carboxylated latex, vinylpyridine latex, and divinylbenzene cross-link SBR.