Styrene butadiene rubber (SBR) is the largest volume synthetic rubber. Compared to natural rubber, SBR has better processability, heat aging and abrasion resistance but is inferior in terms of elongation, hot tear strength, hysteresis, resilience and tensile strength. With over 70% being consumed in the manufacture of tyres and tyre products, demand is very much dependent on the automotive sector.
SBR’s share of total synthetic rubber consumption declined in the 1980s and 1990s as radial tyres, which use less SBR, replaced biased belt tyres. The conversion to radial tyres is essentially complete and should no longer limit growth. On a positive note, growing use low rolling resistance tyres should increase SBR demand.
In non-tyre applications, there has been faster growth in other synthetic rubbers such as ethylene-propylene-diene monomer (EPDM) and nitrile rubbers as a substitute for SBR. However, non-tyre uses for SBR are growing with applications including conveyor belts, gaskets, hoses, floor tiles, footwear and adhesives.
There are two major types of SBR; emulsion SBR and solution SBR, based on different processes. In the past emulsion SBR has been favoured due to its better processing properties while consumers can switch easily between suppliers without any need to reconfigure their processing machines. Emulsion SBR is typically produced on a continuous process making it cost effective.
Solution SBR can be produced on both continuous and batch processes with the batch route allowing for easier ‘fine tuning’ of the reaction conditions and the characteristics of the polymer. Producers of solution SBR have also been improving its processing properties.
Tyre manufacturers, facing increasingly stringent specifications, have found no alternative to solution SBR for the highly specified components in high performance tyres. In addition, the need to reduce fuel consumption has led to the development of low rolling resistance tyres. Since these performance improvements can not be achieved with emulsion SBR, there is a trend towards the increasing use of solution SBR. Dow Chemical says solution SBR is the fastest growing segment of the rubber market with an anticipated growth rate of 5-6%/year over the next several years.
Overall, global growth rates for SBR are predicted be around 2-3%/year. There is a need for more solution capacity as demand is outpacing that for emulsion grade.
Synthetic rubber demand grows
World consumption of synthetic rubber grew by 4.6% in 2006 to reach 12.4m tonnes, compared to 11.9m tonnes in the previous year, and by a further 6.7% in 2007 to 13.2m tonnes, according to the International Rubber Study Group (IRSG). Production increased by 5.0% from 12.2m tonnes in 2005 to 12.8m tonnes in 2006 and by 6.8% in 2007 to 13.2m tonnes. However, world stocks of synthetic rubber have also jumped by 9.4% in 2006 to 3.89m tonnes from 3.55m tonnes in 2005, and by 10.3% in 2007 to 4.28m tonnes.
Synthetic rubber’s share of the total rubber market edged up slightly from 56.7% in 2005 to 57.3% in 2006 and 57.5% in 2007. SBR accounted for 46% of world consumption of synthetic rubber in 2006, according to the International Institute of Synthetic Rubber Producers (IISRP).
However, consumption of synthetic rubber in North America declined 0.5% from 2.228m tonnes in 2005 to 2.217m tonnes in 2006 with the decline accelerating a further 3.5% in 2007 to 2.14m tonnes, according to IRSG statistics. In contrast, synthetic rubber consumption in Asia/Oceania grew 9.4% from 5.24m tonnes in 2005 to 5.73m tonnes in 2006 and by 11.1% to 6.37m tonnes in 2007. The European Union also recorded strong growth in synthetic rubber consumption, increasing by 7.5% from 2.52m tonnes in 2006 to 2.71m tonnes in 2007.
US demand declines
These trends reflect that several large global tyre producers such as Goodyear, Michelin and Continental have expanded or set up new ventures in Asia. There have also been tyre plant closures in the US such as Bridgestone Firestone’s factory in Oklahoma City at the end of 2006. However, demand for tyres produced in Asia is still driven to a large extent by the US and European markets.
The US-based Rubber Manufacturers Association (RMA) projects that tyre shipments in the US will remain close to levels reached in 2007 as growth in replacement markets will again be offset by declines in the original equipment (OE) tyre markets. Combined OE and replacement shipments for the auto and truck categories in 2008 are forecast to increase by fewer than 1m units to 311m total shipments compared to 310.1m units in 2007.
The US market for OE passenger tyres is expected to decline by 4%, or 2.2m units, to nearly 44m units in 2008, according to the RMA. This is a result of expected decreases in domestic vehicle production due to sales trends and a soft economic climate. It also marks the sixth year that light vehicle production has declined in the US. However, the RMA expects a nearly 4% increase in OE passenger tyres shipments in 2009 as the economy stabilises and customers return to a more usual purchasing mode.
The US replacement passenger tyre market was up 4% to 204m units in 2007 as a result of stronger than expected fourth quarter imports, says the RMA. A moderate increase of 1.5%, or around 3m additional units, is forecasted for 2008 as the economic climate dampens growth. A further increase of 2% is anticipated for 2009 as economic conditions improve.
Healthy market for Europe
Demand for SBR in Europe was reported to be healthy in 2007, with the tyre sector performing strongly. The market is balanced to tight with higher prices in Asia pulling product out of Europe. Total SBR demand in Europe is expected to grow around 2%/year with emulsion growing at 1%/year and solution by 4%/year.
The massive build-up of tyre capacity in central and eastern Europe has continued. Manufacturers including Bridgestone, Continental and Pirelli are investing in extra production in Hungary, Romania, Poland, Slovakia and Russia over the next two years.
European SBR producers are facing new EU regulations, due to come in force in 2010, that will prohibit the use of high aromatic oil-extended products in the manufacture of tyres. For vehicles sold in the EU, this means a phased switch from the 1712 grade, specifically for tyres, to grades using other products such as treated distillate aromatic extract.
China drives SBR demand
The growth market in Asia is China. According to China Chemical Reporter, Chinese SBR demand rose 21% in 2006 to reach 747,000 tonnes. However, production only increased 11% to 571,000 tonnes, resulting in imports increasing by almost 60% to 187,000 tonnes.
New SBR capacity is planned for China. Lanzhou Petrochemical started up a 100,000 tonnes/year unit at Lanzhou in March 2008 while Bridgestone is scheduled to start up a 50,000 tonnes/year plant in Huizhou, Guangdong in Q2 2008. Qilu Petrochemical is building a 100,000 tonnes/year facility at Zibo scheduled for early 2009 completion. Other projects include a 100,000 tonnes/year unit being built by Dushanzi Petrochemical in Xinjiang and a 200,000 tonnes/year facility for Fushun Petrochemical in Liaoning, both due for start up in 2010.
Updated: March 2008. Sources: ICB Chemical Profile, 17 March 2008; International Rubber Study Group, Statistical Summary of World Rubber; Rubber Manufacturers Association.