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Renewably-sourced synthetic rubbers are making the cut in the growing automotive and tyre markets, says Angelica Buan in this report.
Cars are one of the greatest inventions of mankind, the best embodiment to man’s appetite for mobility and speed. But what are cars without tyres? Pneumatic tyres, the modern progeny of the earliest tyres made of leather, steel or wood, use synthetic rubber as well as natural rubber. Synthetic rubber has the ability to return to its original shape when stretched or deformed under stress. It also provides tyres their rolling resistance and good grip.
About 60% of the rubber used in the tyre industry is synthetic rubber, hence, demand growth in tyres can be both a blessing and a curse for natural rubber producers because natural rubber only accounts for 40% in tyre production.
Research firm Transparency Market Research (TMR) reiterates that synthetic rubber is the best alternative for natural rubber, in its report spanning the period from 2016-2023. The industry is headed for growth valued at nearly US$46 billion during this period, it says.
Among factors that veer demand from natural rubber to synthetic rubber is the former’s unstable prices, which is caused by “inconsistent supply, geographic constraints on rubber plantations, long transport distances, and rapidly rising demand for rubber across the globe”, according to the report.
Synthetic rubber fills in the lapses from natural rubber, which at the same time help industrial consumers achieve higher profit margins.
In the tyre segment, against the backdrop of regulations continuing to be enforced in favour of environmentally-friendly products, performance demand for environmentally-friendly tyres or sustainable cars produced from renewable resources is a boost to synthetic rubber.
Synthetic rubber from natural sources
The term “natural synthetic rubber” sounds more like a contradiction than a possibility. But new studies on deriving rubber chemicals from natural, renewable sources are proving that contradiction spurs solutions.
Tyre compounds like butadiene are in the forefront of such studies, and the market is more than receptive. Citing findings from Global Markets Insights, the synthetic and biobased butadiene market will surpass US$24 billion by 2024, driven by strong growth in the automotive and tyres segments.
The overall tyre industry size is expanding, estimated to reach nearly 4 billion units by 2024, and thus, spurring ahead the growth of essential raw materials used in tyre manufacturing, such as butadiene. Nevertheless, while synthetic raw materials are benefitting from automotive and tyres market growth, environmental awareness is likewise becoming an important driving force for renewably sourced feedstocks, to have an edge over synthetic, oil-based counterparts.
Markets and Markets in its own report, meanwhile, appraised the butadiene market to be worth more than 16 million tonnes by 2018. It accounts the Asia Pacific region as the world’s largest market for butadiene, which consumed more than half of the total global demand, and also for most of its derivatives that include styrene butadiene rubber (SBR), polybutadiene rubber (PBR), acrylonitrile butadiene styrene (ABS), and nitrile rubber (NR).
China and South Korea are the biggest consumers of butadiene in the region, while India and China are expected to be the fastest growing markets for butadiene, it reported. The region’s high level growth can be attributed to its growing population, which as of 2016 has burgeoned to 4.6 billion, according to the United Nation’sdata.
Developed and developing economies, as well as favourable investment policies and government initiatives, are a few factors that will lead to increased consumption of synthetic rubber and other key materials.
Isoprene from plants
Researchers from the University of Minnesota (UM), University of Massachusetts (UMass), and theCentre for Sustainable Polymers have innovated a new rubber technology, which utilises natural, renewable sources like corn, grasses and trees to obtain isoprene, a chemical compound also known as 2-methylbuta-1,3-diene and which is a chief ingredient in synthetic rubber.
Lead researcher Paul Dauenhauer of UM said that the technology addresses attempts by many tyre companies to find alternative processes for making isoprene from biomass, such as the on-going development of dandelion rubber.
As well, it is a breakthrough proxy to the current process of obtaining isoprene, that is, by thermally breaking up compounds in petroleum through a process called cracking. The isoprene is purified and separated from hundreds of by-products of the cracking process, and then it reacts with itself to develop long polymer chains that are needed to make car tyres.
With the new technology, the researchers described the process of obtaining isoprene from biomass: the first step is the microbial fermentation of sugars, like glucose, obtained from biomass to an intermediate, called itaconic acid. Next, the itaconic acid is reacted with hydrogen to a chemical called methyl-THF (tetrahydrofuran). A unique metalmetal combination developed by the team serves as a highly effective catalyst to optimise this second step. The third step involves the dehydration of methyl-THF to obtain isoprene. Here, the team uses a novel catalyst called P-SPP (Phosphorous Self-Pillared Pentasil). The catalytic efficiency was as high as 90% with most of the catalytic product being isoprene.
UM’s Office for Technology Commercialisation has already applied for a patent on the renewable rubber technology and will license the technology to companies that would like to scale it on a commercial basis. The study was published by the American Chemical Society (ACS) journal, ACS Catalysis.
Embarking on the same venture of obtaining synthetic isoprene is Japanese tyre maker Bridgestone Corporation. The Tokyo-headquartered company announced early this year that it had created synthetic isoprene rubber (IR) through precise molecular structure control, utilising its new proprietary polymerisation catalyst. The newly synthesised IR has the potential to contribute to the development of next-generation rubber with strength and fuel-efficient performance surpassing that of natural rubber, the company stated.
Bridgestone explained that IR is usually manufactured using lithium (Li), titanium (Ti), or neodymium (Nd) catalysts. “The gadolinium (Gd) catalyst we developed is, thus, a completely new innovation,” it said. While it has been known that Gd catalysts have the potential to enable precise control of the molecular structure of IR, it was previously necessary for these catalysts to be used at temperatures below 0°C, which resulted in low activity and made manufacturing processes unfeasible, Bridgestone furthered.
“The Gd catalyst features a structure designed to enable it to be utilised to control IR molecular structure at temperatures above 40°C, the range commonly used in manufacturing processes. Moreover, the new Gd catalyst demonstrates activity of 1,800 cycle/minute, roughly 600 times higher than the activity of conventional Gd catalysts, making its use all the more practical,” Bridgestone added.
Bridgestone said that its IR innovation is part of its goal of working toward making 100% of raw materials used in its tyres sustainable materials by 2050.
Butadiene goes “green”
Scientists from the Catalysis Centre for Energy Innovation at the University of Delaware, US, have discovered a method of deriving an important chemical used in tyres and for other applications, from plant matter.
The process involves turning sugars extracted from switchgrass, wood chips and other biomass into butadiene.
The study, published in the ACS’s scientific journal Sustainable Chemistry and Engineering, is anticipated to extend value for major tyre innovators mentioned like (Goodyear, Michelin (and Bridgestone.
This biobased technology is also deemed to augment the domestic supply of petroleum-based butadiene as demand for automotive use and tyres increases.
The three-step process converts the sugars from woody plants into one compound and then another. The new substance is mixed with a catalyst called phosphorous all-silica zeolite, also invented by the Catalyst Centre, to create butadiene, which the initiators claimed to be similar to that extracted from crude oil.
The Catalyst Centre’s undertaking of producing bioproducts and biofuels is backed by a US$30 million US Federal funding. The team’s work on plant-based butadiene still requires further evaluation of its economic viability and how it can be produced on a commercial scale.
From waste to rubber
In a related development, a research group led by Dr Hassan S Bazzi of the (Texas A&M Universitycampus in Qatar (TAMU-Qatar)has worked on obtaining synthetic rubber from scrap tyres. Through the project, funded by the Qatar Foundation and the Qatar National Research Fund, the team started with cyclopentene, a low value component of petrochemical refining, but which contains hydrocarbons. Working with other experts from the California Institute of Technology, the team toiled around catalysts to string cyclopentene molecules together to make polypentenamers, which are similar to natural rubber.
This heralds cyclopentene as a potential alternative to butadiene that is becoming more expensive and tighter in supply.
The group found that it is possible to achieve a cheaper and energy saving option to conventional butadiene with cyclopentene – by polymerising and degrading it under relatively mild reaction conditions.
The TAMU-Qatar experts said that upon digging further into the feasibility of the synthesis and recyclability of polypentenamer-based tyre additives using equilibrium ring opening metathesis polymerisation, their experimental studies demonstrated that “the concept works very well”. As explained, the researchers polymerised cyclopentene at 0°C, using ruthenium, a transition-metal catalyst; and decomposed the resulting material at 40 to 50 °C.
The team is also currently experimenting on combining synthetic rubber with other tyre materials such as metals and fillers; and determining how the process can viably benefit the tyre industry.