Technology Type

Butadiene and Styrene can be copolymerized in a number of ways. Both ionic and free-radical initiations can be used for this purpose. This fact is re?ected in industrial production of Styrene Butadiene Rubbers (SBRs). Initially the free-radical process was entirely based on hot emulsion processes utilizing a polymerization temperature of 50°C. Later developments showed that much improvement can be made to the product if the polymerization temperature can be lowered to around 5°C. As a result the “cold” emulsion process became the process of choice. Today the cold emulsion process accounts for the larger portion of the emulsion SBR market. Introduction of cold emulsion process and advances in anionic polymerization have demonstrated even further advantages, leading to the introduction of the solution process. The solution SBR products make up a smaller part of the consumption but their volume is increasing. 

Manufacturing of block copolymers is similar to solution SBR process, as they both use anionic polymerization. For elastomeric block copolymers the process is similar to solution SBR process. This is because the same feed puri?cation and reactor layout is needed for producing elastomeric SBR polymers. The main difference between the solution SBR process and block copolymer production process is due to the fact that the styrene monomer distribution in the solution process is random while in block copolymers styrene is present as blocks (sequences of styrene monomer forming a polystyrene segment). In the process styrene and butadiene monomers are charged to the reactors at the same time. In the block copolymer process, ?rst the butadiene segment is polymerized in the absence of styrene monomer. As the conversion of butadiene monomer nears completion, styrene monomer is
added.

Source: Encyclopedia of Polymer Science and Technology, Third Edition, Part 1, Volumes 1−4 Founding Editor Herman F. Mark. Current Volumes Edited by Jacqueline Kroschwitz (J. Wiley & Sons, Inc.). John Wiley & Sons, Inc.:  Hoboken. 2003. 3005 pp.