What Is Buna? From Natural Rubber to Synthetic Rubber
Buna is the term introduced by I.G. Farben for synthetically produced rubber (caoutchouc). In the twentieth century, Buna became an industrially mass-produced article, and particularly with the growth of automobile traffic and motorized warfare, it attained strategic economic and military significance. The acronym Buna originated in late 1927 with the chemist Curt Schumann, who created it from the names of the chemicals used in its synthesis: butadiene and Natrium, the German word for sodium. In 1930, it was given legal protection as a registered trademark of the firm. Since 1929, I.G. Farben had held a patent for the procedure of making synthetic rubber by polymerization: in this case, the bonding of individual molecules (monomers) of butadiene with sodium acting as a catalyst. The German term Kautschuk (caoutchouc) applies to all the elastic polymers from which rubber can be made. Natural caoutchouc, latex, is obtained from the milky sap of the Pará rubber tree (Hevea brasiliensis). Until the early twentieth century, Brazil supplied more than 90 percent of all latex.
In the twentieth century, the chemical industry developed industrial procedures for synthesizing latex by means of polymerization. The chemical composition of latex was determined by Michael Faraday in 1829. In 1879, the French chemist Gustave Bouchardat was the first to make small quantities of synthetic latex by the polymerization process, by heating the unsaturated hydrocarbon isoprene (C5H8) while adding hydrochloric acid. In the early twentieth century, there was a growing demand for latex as a raw material for producing tires for the expanding automobile industry. The rapidly soaring demand could no longer be satisfied, even by extending the areas under cultivation on plantations in the European colonies in Southeast Asia (Malaysia and Indonesia). The price boom led the chemical industry to search for ways to synthesize and process rubber. In Elberfeld, the chemist Fritz Hofmann had been leading development work at the Bayer pharmaceutical laboratory since 1909, working on the compound methylbutadiene (isoprene), which was further processed to become dimethylbutadiene (methyl rubber). The properties of methyl rubber, however, proved unsuitable for tire production.
World War I brought things to a temporary halt. The naval blockade of Germany by the British Navy meant that the country was cut off from imports of natural rubber. Simultaneously, the German chemical industry lost its foreign export markets and shifted its production to accommodate the needs of the wartime economy. Despite initial skepticism, in 1916 Bayer set up in Leverkusen a new production facility for methyl rubber, which made a total of 2,524 tons by 1919. Because of the inferior properties and the high manufacturing costs, which made the synthetic rubber unable to compete with natural rubber in the world market, production of methyl rubber was discontinued after the war’s end.
When progressive motorization caused a jump in the demand for rubber in the United States in the mid-1920s, with a tripling of the price of natural rubber in 1924/25, I.G. Farben decided in 1926 to develop a comprehensive research program on synthetic rubber, to find a marketable procedure for large-scale manufacture based on acetylene chemistry. After the price of rubber plummeted in the world economic crisis and synthesis of latex at competitive market prices became unrealistic, I.G. Farben shut down the majority of its Buna research program in fall 1939. Under the National Socialist regime, however, the firm resumed its plans for large-scale production.
(FS; transl. KL)