Tracing the resiliency of the synthetic rubber industry from its creation to current challenges offers valuable lessons for today's expanding industry
Doris De Guzman/New York
"CIVILIZATION AS we know it today is wholly dependent upon rubber. It is a servant that follows us, literally, from the cradle to the grave."
As the late chemist Ralph Wolf said in the October 1964 issue of Rubber World, nothing has become as ubiquitous and indispensable as synthetic rubber.
A war-born material, synthetic rubber became one of the most important creations of man when the progress of modern civilization was still dependent on the volatility of global natural rubber supply.
In 1906, worldwide natural rubber output was 60,000 tonnes, already an inadequate amount for the rising demand created by the burgeoning automobile industry, according to the 1990 book: Synthetic Rubber - The Story of An Industry, published by the International Institute of Synthetic Rubber Producers (IISRP).
That same year, managers of the German company Bayer decided to offer a price of 20,000 gold marks - an equivalent back then of $5,000 - for a chemist in their company to invent within three years a satisfactory rubber substitute, provided the price of the rubber did not exceed 10 marks/kg.
Just in time, when the price of natural rubber exceeded 26 marks/kg ($3/lb) in 1909, Fritz Hofmann, chief chemist in the Bayer pharmaceutical division, presented the first sample of synthetically produced polyisoprene.
"The isoprene rubber, however, had limited durability. Because of that, Bayer turned its attention to the production of a cheaper methyl rubber in 1910," says Ron Commander, LANXESS' head of the butyl rubber business. The company was formerly Bayer's chemical and polymer business division, which was spun off in 2004.
After 1910, lower natural rubber prices reduced the attractiveness of developing synthetic rubber, according to the IISRP. A pilot plant of methyl rubber from dimethylbutadiene started in 1911, but not until 1915 during World War I did commercial production take place in Germany.
"War was usually the catalyst for sparking interest in synthetic rubber," says Mark Michalovic, consulting historian for the Chemical Heritage Foundation (CHF). "Mechanized warfare requires lots of rubber hoses, belts, gaskets, tires, etc, for tanks, airplanes and such. In World War I, British naval blockades, however, kept Germany from getting natural rubber from Southeast Asia."
Over 24,000 tonnes of methyl rubber were produced between 1914 and 1918, according to the IISRP. The synthetic rubbers were still not very good, says Michalovic, and were only used during that war.
"The Germans knew the rubber was miserably inadequate, as did the rest of the world. With British restrictions on rubber supply and the determination of the US, Germany and the Soviet Union, the synthetic rubber quest was far from over," he says.
VOLATILITY PROMOTES GROWTH
Between 1914 and 1922, natural rubber prices fluctuated from 11.5 cents/lb to as high as $1.02/lb, according to the CHF. Another shortage occurred in 1925, raising the global natural rubber price to $1.12/lb.
With prices rising to over $1/lb, fresh research was undertaken again in 1926 by IG Farbenindustrie (known as IG Farben), a German conglomerate formed in 1925, which included Bayer, BASF, Agfa, Hoechst and other smaller firms.
The US was also looking to develop synthetic rubbers, as by 1925, the country was consuming about 76% of the global rubber supply. The 1930s saw booming new synthetic rubber development and production worldwide, according to historians.
Thiokol, a weak, odorous rubber produced from the mixture of ethylene dichloride and polysulfate, was accidentally discovered by US chemist Joseph Patrick in 1924, and commercial production began in Yardley, New Jersey, in 1930.
Unlike natural rubber, thiokol resists oil and solvents - hence its demand even when it was being sold for 30 cents/lb, about two to three times the price of natural rubber at the time, according to the CHF.
In 1929, US-based DuPont's Arnold Collins developed polychloroprene rubber, now known as Neoprene, which was commercialized in 1933. Several American rubber companies also began to develop copolymer rubbers of their own, such as Goodyear's Chemigum and BF Goodrich's Ameripol. Standard Oil (now ExxonMobil), meanwhile, developed butyl rubber in 1937.
The most notable discovery during the 1930s was when IG Farben's Walter Bock and Eduard Tschunkur polymerized a synthetic rubber called Buna-S from butadiene and styrene in an aqueous emulsion. Now known as styrene butadiene rubber (SBR), Buna-S was being produced in large quantities in Germany by 1935.
IG Farben scientists also developed nitrile rubber Buna-N in 1931, now known as NBR, and began mass production in 1935. For LANXESS, 1937 was a big year for polymer chemistry, says Commander.
"That was when the most important class of antioxidants, antiozonants and antiflex cracking agents was also discovered," he says. "That year, Otto Bayer developed the method that became the basis for polyurethane (PU) chemistry, which led to the development of adhesive raw materials and adhesion promoters."
AN INDUSTRY IS BORN
By 1940, the Soviet Union had the largest synthetic rubber industry - mostly of polybutadiene rubber, according to the IISRP.
With World War II approaching, Germany was rapidly catching up, with production rising from 40,000 tonnes in 1940 to 70,000 tonnes in 1941. The US, meanwhile, barely had 8,000 tonnes of total synthetic rubber output in 1941, with most of it not suitable for tire production.
This fact, not to mention Japan's growing occupation in Southeast Asia, greatly bothered the US government, which led to the formation of the US Rubber Reserve Company (RRC) in June 1940.
"The RRC coordinated synthetic rubber research, development and production among several companies and universities. It was under this program that modern SBR was perfected and most of the first US manufacturing plants were built," says Michalovic.
World War II brought out the best within the rubber and chemical industry, notes Henry Inman, author of the book The Rubber Mirror Reflections of the Rubber Division's First 100 Years. The book is expected out next spring to celebrate the 100th year of the American Chemical Society's Rubber Division.
"You would never see in our lifetime, and even our grandchildren's lifetime, the collaborative efforts that took place at that time with the synthetic rubber program," says Inman. "You have the government, private enterprises and academia all working towards one objective sharing patents and agreements and operating these facilities on behalf of America."
Under the RRC program, all synthetic rubbers produced were given code names, starting with "GR" - for government rubber.
Production of GR-S, the equivalent of Germany's Buna-S, was estimated at 3,271 long tons (3,323 tonnes) by mid-1942, and by 1945 it increased to 756,000 long tons.
"The deal started rollballing around 1943 when the government took control of around 51 plants," says Inman. "The goal was to establish a total of 845,000 long tons/year of synthetic rubber production."
By 1945, synthetic rubber output exceeded 830,000 tonnes/year with the US government financing the construction of 15 SBR plants, two butyl rubber plants, 16 butadiene production facilities and five styrene plants costing about $750m, according to the IISRP.
"Supply was seven times greater than Germany's peak production in 1943," says the IISRP's managing director and CEO James McGraw. "Between 1946 and 1955, most of the plants were later sold to private companies. The next evolution was the rapid expansion in the post-war period, which continued through the 1960s."
STRETCHING TO THE FUTURE
By the mid-1950s, US rubber consumption was divided almost equally between natural and synthetic rubber, while the rest of the world consumed only 10% of synthetics.
Now, synthetic rubber has a larger market share and mostly competes with natural rubber in just a few applications, such as in tires, says McGraw. Around 80% of synthetic rubbers are used by the automotive industry.
"Market share of synthetic and natural rubber has hovered at around 60:40 for the last several years," he says. "While economic forces may influence this ratio, a major shift is not expected unless there is some unforeseen geopolitical event, or an agricultural shift from natural rubber to another more profitable commodity product."
Demand for both natural and synthetic rubber is expected to expand continuously at a strong pace, with the division of the market remaining unchanged throughout 2011.
"Global rubber consumption is forecast to increase by 4%/year to 26.5m tonnes in 2011," the consulting firm Freedonia reports. "Gains will come from solid growth in world motor vehicle production, especially from developing nations such as China, India, Latin America and Eastern Europe."
Synthetic rubber's share in global rubber consumption last year was 58%, according to the International Rubber Study Group (IRSG).
"Global synthetic rubber production last year was estimated at 13.6m tonnes and consumption at 13.2m tonnes," says IRSG economist Dock No. "Global natural rubber production last year was 9.9m tonnes, and consumption at 9.7m tonnes."
US synthetic rubber's average export value last year was $2,012/tonne. Natural rubber's price was $2,321/tonne, says the IRSG.
A significant challenge for the synthetic rubber industry these days, according to McGraw, is the high cost and extremely tight supply of raw materials.
"Shortages have forced some companies to curtail production and this situation could very well be around for foreseeable future," he concludes.
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RUBBER NEEDS CHEMICALS
A report from Oil, Paint and Drug Reporter, October 20, 1941, page 5.
Rubber manufacturers are discovering they are short of a chemical they didn't know they used. It's aniline, and the rubber industry normally takes from 30-40% of annual production. But first it's made into accelerators and antioxidants, and the rubber men get these under various names and never bothered to learn where they came from until defense uses started cutting into the aniline supply.
The rubber men are also being pinched of zinc oxide, which makes up about 1/8 of the weight of many manufactured rubber products. An offsetting factor is the growing use of reclaimed rubber which already contained zinc oxide, carbon black and other chemicals, and so smaller quantities of these are needed in the mix.