Styrene butadiene rubber (BSK, SBR) was one of the first synthetic general-purpose rubbers. Owing to its universal properties, it has hitherto occupied a leading place among all types of synthetic rubber, and its proportion in the general consumption of synthetic rubbers lies at the 36-37% level.
According to a forecast by Grand View Research (USA), the world SBR market by 2020 will reach $US 23 144 billion (8.2 million t), with rates of growth in demand of 6.1% per year [1].
Increase in the demand for SBR in the tyre industry, which covers about 74% of world consumption, has been stimulated by growth of the SBR market. Forecasts by analysts of the International Rubber Study Group (IRSG) and the largest tyre manufacturers point to stable growth and a high demand for new automobiles and tyres. China accounts for a large proportion of growth in demand, and India for a lesser proportion, and in general outlook a period of great potential for all tyre producers will extend to 2020 [2].
The structure of SBR consumption is given in Figure 1.
At present, two technologies are used for the production of SBR in industry: emulsion polymerisation (e-SBR) and solution polymerisation (s-SBR). Each process makes it possible to produce SBR with different characteristics and properties (Table 1).
s-SBR has a narrow molecular weight distribution, less branching in the chain, is lighter in colour, and has a low content of non-rubber substance by comparison with e-SBR. s-SBR has better abrasion resistance, better flexibility and the ability to recover after deformation, and a lower heat generation than e-SBR; their tensile strength, elongation at break, and cost are comparable [3-5].
In recent years, requirements laid down for automobile tyres have changed. Great importance is given to the safety of travel, fuel economy, and ecological safety. One of the rubbers meeting the necessary requirements is solution-polymerised SBR with a medium and high content of 1,2-units. s-SBR gives tyres a unique combination of good wet road holding and low rolling resistance. It is for this reason that s-SBR has gradually started to replace classic e-SBR in tyre manufacture [6].
Actual data on the volumes of production, and even on capacities, are difficult to obtain because many plants at which e-SBR and s-SBR are produced are multipurpose, and, besides these rubbers, depending on the business conditions, other types of rubber can be produced. At e-SBR enterprises, butadiene acrylonitrile rubbers (SKN) and epichlorohydrin rubbers (ECHRs) can be produced, and at s-SBR enterprises, butadiene rubber (PB) and styrene butadiene block copolymers or thermoplastic elastomers (TPEs).
According to data of the International Institute of Synthetic Rubber Producers (IISRP) and manufacturing companies, the world capacities for SBR production amount to 7 250 000 t/year. The structure of the capacities for SBR production by world regions is give in Table 2 [7].
By regions, the SBR capacities are distributed in the following way (percentage of world capacities): Asia/ Oceania--55%, Northern America--15%, Western Europe--11%, Eastern and Central Europe--10%, Latin America--7%, Africa--2%.
The efficiency of e-SBR...