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SBR - Styrene Butadiene Rubber

Styrene-butadiene or styrene-butadiene rubber (SBR) is a synthetic rubber copolymer consisting of styrene and butadiene. It has good abrasion resistance and good aging stability when protected by additives, and is widely used in car tyres, where it may be blended with natural rubber. A chemist called Fritz Hofmann discovered the elastic material methyl isoprene in 1909; many happenings have influenced the development of SR -- the Industrial Revolution, progress of motor transportation, two World Wars, growing demand for rubber and inability of natural rubber (NR) to meet entirely the world elastomer requirements. This synthetic material had opened the door to numerous innovations in previous decades – in automotive engineering, energy generation, medicine, sports, and even the aerospace industry. Industrial manufacture began during World War 2, where it was used extensively by the USA to replace the Far-East natural rubber supplies captured by the Japanese. Its common physical characteristics are - Black in color, other colors can be compounded upon volume special request, 70 +/- 5 Durometer (hardness rating), excellent tensile strength and abrasion resistance at higher temperatures.

SBR can be produced by two basically different processes: from solution (S-SBR) or as emulsion (E-SBR). In the first instance the reaction is ionic polymerisation, in the emulsion polymerization case the reaction is via free radical polymerization. In that process; Low pressure reaction vessels are required and usually charged with styrene and butadiene, the two monomers, a free radical generator and a chain transfer agent such as an alkyl mercaptan and water. Mercaptans controls molecular weight and high viscosity product from forming. The anionic polymerization process is initiated by alkyl lithium and water not involved. High styrene content rubbers are harder but less rubbery.

This copolymer of styrene and butadiene is used in general applications where exposure to mineral oils is not required. Originally developed to replace natural rubber, it performs better at high temperatures, although tensile strength, resilience and abrasion resistance are inferior at lower temperatures. SBRs have inferior weathering and chemical resistance to most other elastomers.

Asahi Kasei, Lanxess, LG Chem, Polimeri Europa, Sinopec and are some of the leading producers of SBR in the world. Bangkok Synthetics (BST), Nanjing, China, Tianjin, China, Northwest China, Jurong Island, Singapore, Quanzhou, China, Dongming, China are some of the companies who have announced capacity expansions in SBR from 2012 to 2014. Global capacity of SSBR in 2011 was 1.2 MMT and is expected to touch 1.9 MMT.

In 2011 SBR capacity in India was 0.02 MMT and is expected to touch 0.37 MMT in 2016. There are capacities planned in SBR and Butyl rubber during 12th 5 year plan period. This, to some extent would mitigate substantial short-fall in domestic non-availability of synthetic rubber India’s first large-scale styrene butadiene rubber (SBR) plant will be built at Panipat by Indian Synthetic Rubber – a joint venture among IndianOil Taiwan’s TSRC and Japan’s Marubeni. An estimated $200m (€142m) is being spent on the 0.12 MMT SBR plant, which is scheduled for completion in 2013. Reliance Industries Ltd and IOCL are planning capacity additions and by 2016 SBR capacity of these two players is expected to touch 0.15 MMT and 0.2 MMT respectively.

Typical applications are sealing requirements for hydraulic braking systems. Additionally, it is used in some rubber cutting boards.

The elastomer is used widely in pneumatic tires, shoe heels and soles, gaskets and even chewing gum. It is a commodity material which competes with natural rubber. Latex (emulsion) SBR is extensively used in coated papers, being one of the most cost-effective resins to bind pigmented coatings. It is also used in building applications, as a sealing and binding agent behind renders as an alternative to PVA, but is more expensive. In the latter application, it offers better durability, reduced shrinkage and increased flexibility, as well as being resistant to emulsification in damp conditions.

SBR can be used to 'tank' damp rooms or surfaces, a process in which the rubber is painted onto the entire surface (sometimes both the walls, floor and ceiling) forming a continuous, seamless damp proof liner; a typical example would be a basement.

1. Emulsion Polymerization of SBR:

Typically, an emulsion system for polymerization contains water, monomer, initiator, and an emulsifier. The polymerization process was initially done at 50 degrees celsius, but improved technology allowed for “cold” processes to be developed with reaction temperatures at 5 degree celsius. The polymerization of cold SBR is initiated by the reaction of a hydroperoxide with ferrous icons, which furnishes free radicals for polymer formation. Polymerization is stopped at 60 percent conversion with a short stop agent such as hydroquinone. Higher conversion percentages generally lead to polymers with inferior physical properties, most likely due to unwanted chain cross-linking. The latex is warmed, and the excess butadiene and styrene is recovered for recycling by either steam stripping or distillation.

2. Solution Polymerization of SBR:

The processes to produce SBR & PBR by solution are very similar. A catalyst is added to a thoroughly dried mixture of monomer and hydrocarbon solvent. After reacting and polymerizing in one or more reactors, a shortstop is added to limit the conversion of the polymer.

3. Emulsion Polymerization of SBR:

Typically, an emulsion system for polymerization contains water, monomer, initiator, and an emulsifier. The polymerization process was initially done at 50 degrees celsius, but improved technology allowed for “cold” processes to be developed with reaction temperatures at 5 degree celsius. The polymerization of cold SBR is initiated by the reaction of a hydroperoxide with ferrous icons, which furnishes free radicals for polymer formation. Polymerization is stopped at 60 percent conversion with a short stop agent such as hydroquinone. Higher conversion percentages generally lead to polymers with inferior physical properties, most likely due to unwanted chain cross-linking. The latex is warmed, and the excess butadiene and styrene is recovered for recycling by either steam stripping or distillation.
       

Capacity (kt) Actual Projected
2011-12 2012-13 2013-14 2014-15 2015-16 2016-17
RIL 0 0 75 150 150 150
IOCL 0 0 60 120 200 200
Eliokem 10 10 10 10 10 10
Apcotex 10 10 10 10 10 10
Total 20 20 155 290 370 370

Producer SBR: India Demand Supply
Actual Projected
2011-12 2012-13 2013-14 2014-15 2015-16 2016-17
(kt)  
Capacity 20 20 155 290 370 370
Prod/Cons 20 20 155 290 370 370
Imports 170 182 87 0 0 0
Exports 8 4 27 60 119 95
Consumption 186 198 215 230 251 275
             
Cons Growth (%)   6% 9% 7% 9% 10%

 
 
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