Styrene Butadiene Rubber

The most important Synthetic Rubber and the most widely used Rubber in the entire world is SBR, a copolymer of styrene and Butadiene. The hisory of developement of SBR could be traced of World War II, when the first commercial production of SBR (called GR-S at that time) first started. Butadiene and Styrene are the chief raw materials required to manufacture SBR. Others required in small quantities are various emulsifiers, modifiers, catalysts, short stops, coagulating agents, antioxidants and antiozonants. While SBR is manufactured by both emulsion and solution polymerisation methods, the more popular and predominant grades are manufactured by emulsion polymerisation

Monomer Sources

Butadiene

Two types of processes have been used for the large scale production of Butadiene.

1) Those which use petroleum derived C4 hydro-carbons as the starting materials and,

2) Those which use Ethyl Alcohol as the starting material.

Processes of the first type fall into three broad classes :

(a) Those in which Butadiene is produced from n-Butanes.

(b) Those in which Butadiene is produced from n-Butanes.

(c) Those in which Butadiend is produced - directly by steam cracking of Naphtha and gas-oil petroleum fractions.

1. Production of Butadiene from n-Butanes

The n-Butanes are obtained from C3-C4 stream from the cracking of petroleum crudes. Propane and Iso-Butane are separated by fractionation and Isobutane is removed by absorption in 65% - Sulphuric Acid. The stream is then subjected to catalytic dehydrogenation using catalyst as mixed calcium-nickel phosphate stabilised with chromum oxide.