Market Topics

Synthetics Generate a Buzz


Synthetics Generate a Buzz

Conventional base oils are the backbone of 90 percent of the worlds lubricants. Theyre familiar, reliable and widely available.

For more demanding performance or environmental needs, though, formulators must look to the exotic chemistry set known as API Group V base oils. This umbrella category includes naphthenics, a spectrum of pricey synthetics, and biobased fluids. The Group V category is also where youll find a fresh wave of base oils promising both enhanced performance and sustainability, so customers can lubricate well while doing good.

Delegates to the Society of Tribologists & Lubrication Engineers annual meeting in May got a closer look at one of these products, a renewable base oil called Entrada-base, made by the Canadian company Advonex Inter­national. Derived from soybean oil, Entrada-bases 4 centiStoke grade has an impressive 150 viscosity index, a pour point of -18 degrees Celsius, and less than 9 percent Noack volatility. With those sparkling numbers, it is being positioned to compete in the marketplace as an API Group III+, CEO Chad Joshi revealed at the companys trade booth during the meeting.

Originally called Altranex but rebranded as Advonex in 2016, the company partnered with farm cooperative Minnesota Soybean Processors to develop its products. But Joshi emphasized that its patented processes are feedstock agnostic; they can build up stable, long-chain molecules from any renewable oil-soy, canola, coconut, palm, even used cooking oil, he said.

In a presentation at STLE, scientist Sun Lee explained that instead of solvent refining or hydroprocessing petroleum, Advonex uses a three-step process to rearrange oilseed molecules. First comes fat-splitting, where the plant oils triglycerides are converted into free fatty acid anions. Electrolysis comes next, she explained, to expel the oxygen radicals and knit the remaining atoms into long-branched hydrocarbons up to C50 in length. Last comes hydrofinishing to yield stable and highly pure wax, gel, white oils or base oil, depending on the feedstock.

The company has been working with Valvoline to demonstrate the renewable Group III+ oils performance in motor oil. Lee described two SAE 5W-30 products having Entrada-base at 50 percent and 41 percent of the formulations, and a conventional additive package. With a minimal amount of pour point depressant (0.05 percent), the products boast a pour point of -42 C, as well as the high-temperature endurance, cold cranking and high-temperature high-shear rate viscosity expected for a top-tier motor oil.

Advonex last September moved past the R&D stage and began building a 12,000 square foot pilot manufacturing facility in Elizabethtown-Kitley, Ontario. It next will construct full-scale units there, with commercial production expected next year. Besides lubricants, it is targeting its output to the the high-value personal care, cosmetics, coatings and wax markets.

PAG Plays Nice

Another new base oil, this one targeting heavyweight applications, comes from BASF in Germany. Speaking in January to the 21st International Colloquium Tribology at the Technische Akademie Esslingen, the companys technical marketing manager for base stocks, Frank Rittig, observed that lubricant formulators options for thickening industrial gear oils include high viscosity grades of polyalphaolefin, polyisobutene, polyalkyl methacrylate and polyalkylene glycol.

Formulators want to see a performance profile with classic properties like non-toxicity, stability and ease of handling, he said, and some may have additional requirements like shear stability and total cost of thickening. Blenders also want to be able to demonstrate cost reductions from wear and friction, and savings in energy and equipment life for their end-use customers.

Heavyweight PAGs might have filled the bill as a thickener, Rittig said, but unfortunately most PAGs are not miscible with either mineral oil or PAO. Compatibility with API Groups I through IV is a must, he said, plus high viscosity and low friction properties.

He then pointed to BASFs newest PAG molecule, which overcomes the miscibility issue with a unique hybrid chemical structure. The company has developed two variants, XPB 184 and XPB 171, with 227 and 194 viscosity index, respectively. Made at its Verbund manufacturing site in Ludwigshafen, these base stocks have noteworthy pour points of -39 and -37 C, respectively.

The companys research­ers checked XPB 184s compatibility with a wide range of other base stocks, including multiple Groups I, II and III, PAO, esters and more. Mixed into each sample at doses of 10, 50 and 90 percent, and then held at 60 C for over four weeks, the new PAGs remained in solution without clouding or separating. Each is compatible with mineral oil, PAO 6 and PAO 40, naphthenic base oil and alkylated naphthalene, Rittig declared. Somewhat ironically, the new fluids are not miscible with conventional PAG due to issues with polarity.

He went on to highlight mini-traction coefficient tests results showing that, in combination with PAO or metallocene PAO, this new technology can allow formulators to achieve about a 30 percent reduction in friction versus neat PAO. BASF calls the new chemistry EEB, for energy efficient base stocks, and while he declined to disclose the production process or molecular structure, Rittig pointedly asserted that EEB differs materially from the patented, oil-soluble PAG that Dow Chemical sells under the trademark OSP.

Making the Eco Case

Another speaker at the tribology colloquium, Frankfurt-based David Schaffel, who is responsible for the EMEA region for Clariant, took base stock sustainability as his topic. Making the case for petroleum-derived PAGs, Schaffel pointed to preliminary results from a life cycle analysis that covers both the production and usage phases of these lubricants.

Promoting sustainability makes good business sense for lubricant companies, he remarked. Large corporations are publishing sustainability reports with as many pages as their annual reports. And eco-labels such as the Blue Angel in Germany, the Nordic Swan and others, already look at renewability of raw materials. But, is something renewable necessarily better? Not all the data is in yet from our study, but we believe we have sufficient data to suggest an interesting outcome, Schaffel said.

Life cycle analysis evaluates a products environmental impact and proceeds through four stages: goal definition and scope, inventory analysis, impact assessment and interpretation of the results. Its highly complicated, Schaffel conceded. For example, if one were baking a cake, the inputs would include the production process (the oven) and the energy needed, plus the ingredients-flour, eggs, milk-as well as the cow that produced the milk, the crop that fed the cow, and the fertilizer that went onto the crop, and so on. The impact of each input then is compared with the alternatives, so the most environmentally responsible choice can be made.

Rather than a cake, Clariants ongoing study is evaluating a PAG, a PAO and a mineral oil in a typical industrial setting: a polymer extruder that requires 70 liters of lubricants a year and runs at an average engine power of 200 kilowatts. To measure the impact of various lubricants in this application, Schaffel said, you need to look at the raw material and polyglycol production process; the lubricant gear oil formulation and those raw material inputs; the lubricant distribution process, the lubricants use, and the end-of-life disposal.

Although some renewable, biobased PAGs have appeared in the market, Clariant studied only petroleum products, because peer-to-peer comparisons are one of the fundamental principles of life cycle analysis. The test is tracking a D21/150 PAG, where 21 and 150 indicate the ethylene oxide/propylene oxide ratio. Cradle-to-grave analysis then has to consider all the steps for making the ethylene oxide and the propylene oxide, the energy needed, the utilities and water, etc.

While the final results are not in yet, compounded formulations of three ISO VG 220 fluids, made with mineral oil, PAO and PAG, have undergone the FZG gear energy efficiency (lost-torque) test. Here, the PAG showed large enough energy savings in the usage phase to more than offset the electricity consumed in manufacturing the PAG, Schaffel pointed out. More results will be presented as theyre available, to strengthen the case for PAG sustainability and energy efficiency, he added.

Ester Secrets

Strides are also being made in synthesizing better plant-based esters for lubricants, Svajus Asadauskas, of Lithuanias Center for Physical Sciences & Technology, reported to the TAE meeting. Along with his colleagues Linas Labanauskas and Karolis Petrauskas, he has been investigating whether plant esters have specific advantages beyond biodegradability alone.

Natural materials like castor, jojoba, animal fats and sperm whale oils have a long history as lubricants, he continued, but they suffered from inconsistencies in supply, uniformity and performance. For example, jojoba oil flows well in its native warm climate, but is not as good in colder temperatures. Soy, corn, palm and canola were harnessed more recently, but the latest thinking is that industrial uses should not compete with humans for food crops.

This has led to the European Unions COSMOS project, a tortured acronym standing for Camelina & crambe Oil crops as Sources for Medium-chain Oils for Specialty oleochemicals. This ambitious program aims to reduce the regions need to import tropical oils like palm, coconut and others. It hopes to turn native plants like crambe and camelina into profitable oilseed crops, and use their oils in high-value lubricants, surfactants and polymers.

As Asadauskas explained, camelina, non-edible rapeseed and crambe are extraordinarily rich in very-long-chain fatty acids (C20 and greater), which can be converted via a metathesis process called ethenolysis into medium-chain fatty acids (C10 to C14). Such chain lengths are highly suitable for making hydraulic fluids-a crucial point, because hydraulic fluids tend to be lightly additized and must depend heavily on the base oil for their performance.

Vegetable oil based hydraulic fluids are already used in many places, but most biobased esters are unsaturated, and unsaturation is viewed as a problem for hydraulic fluid stability, Asadauskas said. Some unsaturated oils (poly-unsaturated in particular) indeed can undermine a lubricants oxidative stability, heat capacity and hydrophobicity. However, unsaturation also boosts lubricity, thermal conductivity, biodegradability and tribofilm formation.

CPST researchers have been testing three innovative plant-ester base oils-saturated polyol esters, unsaturated derivatized esters and mono-unsaturated dibasic acid esters-and probing the role of unsaturation in their performance.

Working with small lab-made samples, and using non-food ester for at least 50 percent of the final base oil content, their target was to make an ISO VG 32 hydraulic oil having a pour point below -30 C. The scientists found that mono-unsaturation was strongly linked to gains in both viscosity index and pressure-viscosity coefficient. Together these two properties make for greater separation between moving surfaces and much less wear.

In pour-point tests, the researchers also saw mono-unsaturated oils as having a beneficial effect on low-temperature fluidity versus the rivals.

These promising compounds are moving towards commercialization, with patents pending for the mono-unsaturated types. Asadauskas suggested they may help reduce hydraulic equipment operating temperatures, because the unsaturation contributes to thermal conductivity. And while operating temperature always must be considered, he believes the esters innately high V.I. will assure better hydraulic fluid service life.

Related Topics

Market Topics