Lithium prices have skyrocketed since mid-2016 and grease manufacturers have found it difficult to secure lithium hydroxide, a key raw material for making lithium greases. Their woes are unlikely to end soon unless they find thickener alternatives to lithium soap, industry officials said at the annual conference of the National Lubricating Grease Institutes India Chapter, in Varanasi, India.
Over the last four decades, conventional lithium and lithium complex soaps have thickened the main multipurpose greases for various automotive and industrial applications. Competition for raw materials from other industries has been fierce, however, as lithium has witnessed a buying frenzy from electric car manufacturers and other technology companies in the United States, Europe and China, all vying to secure supplies for production of lithium-ion batteries.
In 2016, battery manufacturers were the largest end users of lithium at 39 percent, followed by ceramics and glass producers at 30 percent and lubricating greases at 8 percent, according to the United States Geological Surveys Mineral Commodity Summaries 2017.
Approximately three quarters of the worlds grease supply is thickened with lithium soap. Global production of lithium and lithium complex greases totaled over 836,000 metric tons in 2015, according to the NLGI Grease Production Survey. India leans on lithium particularly heavily. Ninety-one percent of the countrys grease production or close to 69,000 tons, was thickened with lithium soap, out of a total of 75,500 tons of grease produced in the country, the survey showed.
The major reasons for the popularity of lithium-based greases are that they have good shear stability, excellent water resistance, high temperature capability and good response to various additives, Vijay Deshmukh, general manager of research and development at Standard Greases & Specialities, said during the conference held in early February.
However, theres a high probability that costs for lithium hydroxide will continue to increase, and the ready availability of alternative chemistries would help mitigate the impact, he noted.
Lithium, dubbed white petroleum for its silver-white color, is available in abundance in the earths crust, but mining the metal at a competitive price and in useful form is a challenge. Subsurface brines, which are the major source material for lithium carbonate, are less expensive to mine than rocks such as spodumene, petalite and other lithium-bearing minerals.
Lithium becomes useful only after it has been extensively refined into either lithium carbonate or lithium hydroxide, two of the forms in which the metal is purchased and sold in the market. According to London-based battery minerals data provider Benchmark Mineral Intelligence, the BMI Lithium Price Index surged 66 percent in 2016, based on trading data of both lithium carbonate and lithium hydroxide.
Eltepu Sayanna, president of NLGIs India Chapter, said the grease industry in India has been under turmoil over the supply and pricing of lithium hydroxide. Indian grease makers are completely dependent on imports, as the country doesnt have native sources to draw upon. It has compelled grease manufacturers to look beyond the obvious and search for suitable alternatives for the same, he noted.
Determining Suitable Alternatives
Depending on the end applications, operating conditions and cost economics, suitable thickeners can be selected as alternatives to conventional lithium and lithium complex, Deshmukh stated. These include anhydrous calcium, aluminum complex, calcium sulfonate complex, calcium complex, barium complex, sodium complex, mixed base greases and polyurea.
Worldwide production of these alternatives is somewhat limited compared to lithium soap. The more sophisticated calcium types (such as anhydrous calcium, calcium sulfonate and calcium complex greases, for instance) added up to nearly 72,000 tons of the greases manufactured worldwide in 2015, according to the NLGI survey, representing 6.4 percent of total grease production.
Polyurea followed with a little over 66,500 tons (6 percent), more than two-thirds of that limited to Japan, North America and Europe.
Aluminum complex greases accounted for almost 40,000 tons (3.5 percent), and sodium complex grease production was under 5,000 tons. Barium complex grease falls under the Other Metallic Soap category of the survey, which totaled just over 14,000 tons.
Standard Greases tested some of the alternative thickeners in grease samples using ASTM International and Institute of Petroleum specifications, then compared the results with the Bureau of Indian Standards stipulations for conventional lithium grease and lithium complex grease, said Deshmukh. The BIS is an autonomous national standards body in India.
Results showed that some of the alternatives were more promising than others. Anhydrous calcium greases showed excellent water and corrosion resistance, good shear stability, a dropping point of 144 degrees Celsius and a maximum operating temperature of 90 C, versus 120 C for lithium grease meeting Indias IS:7623 standard, he noted.
Aluminum complex, polyurea and calcium sulfonate greases also were tested against the IS:14847 specification for lithium complex grease in industrial applications. Aluminum complex greases have a high dropping point, temperature stability, good water resistance, excellent pumpability due to their small particles, and corrosion resistance, he said. These properties make them the most suitable greases in steel plant applications, especially in centralized lubrication systems, he added.
Calcium sulfonate complex-thickened greases have high performance without the need for additives, but can be enhanced with additive treatment. These greases show a very high dropping point of 300 C (against 260 C in lithium complex greases), strong extreme pressure and antiwear performance, rust protection, high temperature resistance, and mechanical and shear stability, stated Nilesh Kadu of Lubrizol India in his conference presentation.
Calcium sulfonate complexgreases can be used in high temperature, wet and heavy-load conditions in mining, marine, food grade and off-highway applications, Kadu added. The major downside is that they have poor low-temperature pumpability.
Polyureas, used primarily for greases in automotive applications, such as wheel bearings, present a high dropping point, oxidative stability, good water resistance, shear stability and long service life. They also have good flow properties, making them suitable for centralized lubrication systems. These greases are used in demanding industrial applications, as well.
Polyurea grease has good scope for standardization of manufacturing procedure to make it a cost-effective alternate to lithium complex grease, Deshmukh stated.
However, the handling of toxic raw materials is a major concern in manufacturing of polyurea, he added. They are also hindered by poor mechanical stability and storage hardening, and they require additives for rust and corrosion protection as well as extreme pressure performance.
Sodium complex greases have a high dropping point but poor water resistance, which makes them ideal only for applications with no ingress of water, said Deshmukh. Calcium complex soap allows for manufacturing of high temperature resistant and extreme pressure grease, but hardens while in storage, making transport difficult.
Barium complex greases are used in special applications requiring synthetic oils, such as high speed bearings in computer-controlled cutting machines. These greases have a high dropping point, good water resistance and excellent adhesiveness to metal surface. However, due to their toxicity, they are not popular as general purpose greases, noted Deshmukh.
Among mixed base greases, he mentioned the most popular is lithium-calcium grease. Replacing part of the lithium with calcium produces the added advantage of higher water resistance, without affecting the greases other properties. The addition of calcium soap makes the grease cost effective compared to exclusively lithium based grease.
Measuring the Downsides
The total cost, availability and safety of these alternative greases are some of the factors that manufacturers will have to consider before replacing conventional lithium and lithium complex soap thickeners, Deshmukh advised. You cant have a single substitute for lithium complex greases, he said.
In India, production of calcium sulfonate greases represented just under 1,000 tons, 1.4 percent of total production in 2015, according to the NLGI report. Aluminum complex grease production came in under 50 tons, and polyurea accounted for a mere 1.6 tons. There was no local production of calcium complex or anhydrous calcium greases in the country.
The raw materials for all these alternatives are readily available and sourced locally, except for one particular component of the aluminum complex thickener called aluminum isopropoxide, which is imported, Deshmukh told LubesnGreases.
Tariffs and taxes on the imports of raw materials do add to the overall cost of manufacturing these alternatives, but are already included in the price quoted by importers, he added.
Polyureas presence in India is minor due to limits on production in the country. Polyurea greases are manufactured using isocynates and amines, and the toxic nature of these components restricts their large-scale manufacture. However, the finished grease can be used in many food grade applications, Deshmukh said.
In general, the cost of producing alternative greases, such as those thickened with aluminum complex, polyurea and calcium sulfonate complex, would be on par or 10 percent higher than that of lithium complex grease based on the current cost of lithium hydroxide, Deshmukh added.
But the most important thing is that these alternatives must be tried and established over a long period of time, Deshmukh emphasized.