Polybutadiene [butadiene rubber, BR] is a synthetic rubber. It offers high elasticity, high resistance to wear, good strength even without fillers, and excellent abrasion resistance when filled and vulcanized. "Polybutadiene" is a collective name for homopolymers formed from the polymerization of the monomer 1,3-butadiene. The IUPAC refers to polybutadiene as "poly(buta-1,3-diene)". Historically, an early generation of synthetic polybutadiene rubber produced in Germany by Bayer using sodium as a catalyst was known as "Buna rubber". Polybutadiene is typically crosslinked with sulphur, however, it has also been shown that it can be UV cured when bis-benzophenone additives are incorporated into the formulation. Polybutadiene rubber (BR) accounted for about 28% of total global consumption of synthetic rubbers in 2020, whereas styrene-butadiene rubber (SBR) was by far the most important grade (S-SBR 12%, E-SBR 27% of the entire synthetic rubber market). It is mainly used in the manufacture of tires, which consumes about 70% of the production. Another 25% is used as an additive to improve the toughness (impact resistance) of plastics such as polystyrene and acrylonitrile butadiene styrene (ABS). Polybutadiene is also used to manufacture golf balls, various elastic objects and to coat or encapsulate electronic assemblies, offering high electrical resistivity.
History
The Russian chemist Sergei Vasilyevich Lebedev was the first to polymerize butadiene in 1910. In 1926 he invented a process for manufacturing butadiene from ethanol, and in 1928, developed a method for producing polybutadiene using sodium as a catalyst. The government of the Soviet Union strove to use polybutadiene as an alternative to natural rubber and built the first pilot plant in 1930, using ethanol produced from potatoes. The experiment was a success and in 1936 the Soviet Union built the world's first polybutadiene plant in which the butadiene was obtained from petroleum. By 1940, the Soviet Union was by far the largest producer of polybutadiene with 50,000 tons per year. Following Lebedev's work, other industrialized countries such as Germany and the United States developed polybutadiene and SBR as an alternative to natural rubber. In the mid-1950s there were major advances in the field of catalysts that led to the development of an improved versions of polybutadiene. The leading manufacturers of tires and some petrochemical companies began to build polybutadiene plants on all inhabited continents; the boom lasted until the 1973 oil crisis. Since then, the growth rate of the production has been more modest, focused mainly in the Far East. In Germany, scientists from Bayer (at the time a part of the conglomerate IG Farben) reproduced Lebedev's processes of producing polybutadiene by using sodium as a catalyst. For this, they used the trade name Buna, derived from Bu for butadiene, Na for sodium (natrium in Latin, Natrium in German). They discovered that the addition of styrene to the process resulted in better properties, and thus opted for this route. They had invented styrene-butadiene, which was named Buna-S (S for styrene). Although the Goodrich Corporation had successfully developed a process for producing polybutadiene in 1939, the U.S. federal government opted for the use of Buna-S to develop its synthetic-rubber industry after its entry into the World War II, using patents of IG Farben obtained via Standard Oil. Because of this, there was little industrial production of polybutadiene in America during this time. After the war, the production of synthetic rubber was in decline due to the decrease in demand when natural rubber was readily available again. However, interest was renewed in the mid-1950s after the discovery of the Ziegler–Natta catalyst. This method proved to be much better for tire manufacturing than the old sodium polybutadiene. The following year, Firestone Tire and Rubber Company was first to produce low cis polybutadiene using butyllithium as a catalyst. The relatively high production costs were a hindrance to commercial development until 1960 when production on a commercial scale began. Tire manufacturers like Goodyear Tire and Rubber Company and Goodrich were the first to produce plants for high cis polybutadiene, this was followed by oil companies like Shell and chemical manufacturers such as Bayer. Initially, with plants built in the United States and France, Firestone enjoyed a monopoly on low cis polybutadiene, licensing it to plants in Japan and the United Kingdom. In 1965, the Japanese JSR Corporation developed its own low cis process and began licensing it during the next decade. The 1973 oil crisis marked a halt to the growth of synthetic rubber production; the expansion of existing plants almost ceased for a few years. Since then, the construction of new plants has mainly taken place in industrializing countries in the Far East (such as South Korea, Taiwan, Thailand, and China), while Western countries have chosen to increase the capacity of existing plants. In 1987, Bayer started to use neodymium-based catalysts to catalyze polybutadiene. Soon thereafter other manufacturers deployed related technologies such as EniChem (1993) and Petroflex (2002). In the early 2000s, the synthetic rubber industry was once again hit by one of its periodic crises. The world's largest producer of polybutadiene, Bayer, went through major restructuring as it was troubled by financial losses; between 2002 and 2005 it closed its cobalt-polybutadiene plants in Sarnia (Canada) and Marl (Germany), transferring their production to neodymium plants in Port Jérôme (France) and Orange (USA). During the same time, the synthetic rubber business was transferred from Bayer to Lanxess, a company founded in 2004 when Bayer spun off its chemicals operations and parts of its polymer activities.
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