Predicting the Future of Additive Package Components
Additive companies play a large role in the drive for better fuel economy and reduced emissions, impelled by legislators and engine makers. Philip Reeve gives a roundup of the trends that lie ahead for additive technology.
Emerging new lubricant requirements for crankcase engines will drive formulation changes. Some component types used in additive packages will be in greater demand, and some will decline over the longer term. Knowing what is in store is important to plan future research and development work and investment for both additive packaging companies and component suppliers.
In the next decade, lubricant formulations for internal combustion engines will be driven by environmental regulations, particularly fuel economy and emissions control. They are targeted to reduce carbon dioxide, sulfur and nitrogen oxides and particulates to improve air quality. Industry bodies and original equipment manufacturers continually make changes to vehicle hardware to meet new regulations. New specifications and modified lubricant formulations then follow to provide protection for the latest passenger car, motorcycle, marine and heavy-duty diesel engines.
The major trends affecting future component requirements are increasing oil drain intervals, smaller sump levels, higher running temperatures and smaller engine capacities, all of which put increased oxidative stress on the lube oil, Philip Collier, sales and business development manager at South Korean chemicals company Songwon Industrial Group, told LubesnGreases.
Some lubricant chemical restrictions are aimed at protecting emissions control systems by limiting levels of sulfated ash, phosphorus and sulfur, known as SAPS. The introduction of lighter viscosity grade products supports improved fuel economy; however this creates new challenges to the formulator to ensure satisfactory durability.
Future chemical regulations could also be important – tetra-propenyl phenol now, but other materials containing molybdenum, boron or zinc may be impacted in future, Alisdair Brown, technology director at additive manufacturer Afton Chemical, told LubesnGreases.
In 2020, marine lubricants will need to adapt to a stricter cap on sulfur levels in marine fuel. specification. Changes in lubricant formulations will require modified additive package technology and changes in demand for certain component types. Which component types are likely to grow and which to decline?
Ashes to Ashless
Ashless dispersants are used primarily in passenger car, motorcycle and heavy-duty diesel crankcase oils. They help prevent sludge, varnish and other deposits from forming on critical surfaces. They also control viscosity increase from soot formed during the combustion process, which makes its way into the crankcase oil.
Dispersants typically are a major volume component, making up 30 to 60 percent of the additive package for automotive oils. As lubricants move to lower viscosity for enhanced fuel economy, the thickness of polymeric-based dispersant becomes more problematic.
Rolfe Hartley of Sangamon Consulting said: The trend is to maximize fuel economy by minimizing the oil viscosity. Use of high treats of thicker dispersant complicates formulating lubricants meeting low temperature properties in fuel economy viscosity grades. It drives formulators to use lighter base stocks, resulting in higher volatility lubricants.
Dispersants do not run up against chemical restrictions although treat rates may be restricted by seals compatibility tests. They will remain critical components for future formulations and demand is expected to stay stable or grow. For future enhancements, there is a need for a diesel soot dispersant of lower viscosity to facilitate formulation of fuel economy grades. This would allow a substantial reduction in treat rate, package viscosity and would greatly enhance formulation flexibility in finished oils, Hartley said.
The majority of metallic detergents are based on either calcium or magnesium attached to an oil-soluble organic soap, typically sulfonate, phenate or salicylate-carboxylate. Overbased detergents have an alkali core that provides a base number and neutralizes acidic combustion and oxidation byproducts. A detergents primary function is to control deposits in the engine and reduce corrosion and rust. It may also have secondary benefits, such as oxidation inhibition.
The largest market for overbased metallic detergents is in marine engine oils. A key impact to the industry is the International Maritime Organizations 2020 marine fuel regulation. This mandates a reduction in the sulfur limit of marine fuels in open waters from 3.5 percent to a 0.5 percent maximum from Jan. 1, 2020. Its aim is to significantly reduce air pollutants from ships, particularly sulfur oxides. This change will result in much less overbased detergent being required as there is less acid from the sulfur oxides to neutralize. Shell Marine, for one, has already launched a new product at lower base number, ahead of the regulations introduction. On the other hand, there is still uncertainty about the availability of the new fuels and higher base number formulations will continue to be satisfactory.
For passenger car lubricants, Hartley notes, to meet the challenge of ever increasing requirements for fuel economy, there has been a convergence in formulations toward detergent systems containing calcium.
However, the latest passenger car gasoline specifications (API SN Plus, introduced in 2018, and ILSAC GF-6 scheduled for 2020) contain tests designed to protect new gasoline direct injection engines from low-speed pre-ignition. This tends to limit the calcium level and favor a move towards more magnesium-based detergents.
Finally, European Automobile Manufacturers Association specifications have limits on the maximum sulfated ash level allowed in lubricants primarily to protect against exhaust filter blockage. Magnesium can provide a higher total base number per unit of sulfated ash and so tends to be favored in applications where high total base number is important. As calcium and magnesium are both major sources of ash in lubricants, this also tends to limit any growth in detergent demand through higher treat rates.
Propping Up the Zinc
Zinc dialkyldithiophosphates have been a mainstay of automotive engine oils for several decades, providing a cost-effective source of wear protection and antioxidancy. ZDDPs contribute SAPS in the lubricant, and it is these chemical parameters that are restricted in newer formulations.
Demand for ZDDP is likely to remain stable with the possibility of a reduction in the future. ZDDPs have many positive performance attributes. However, [they] run up against the chemical box restrictions now imposed by many of the industry and OEM specifications to protect expensive and sensitive emission systems, Andrew Ogley, chief chemist at United-Kingdom-based fuel and lube additive company SBZ Corp., told LubesnGreases.
It is possible to formulate with very low ZDDP levels, for example, passenger car engine oils meeting ACEA C1 quality with a maximum phosphorus level of 500 parts per million.
With chemical restrictions on higher treats of ZDDP, but greater thermal and oxidative pressures on the oil, supplementary antioxidant and antiwear components provide a way for formulators to improve quality levels.
We certainly expect to see further increases in demand for antioxidants driven by these factors…We believe there is more performance possible from synergistic combinations, for example phenolic-aminic, for certain applications. However, there is a need for innovation in antioxidants, Jun Dong, Songwons lubricants technology manager, told LubesnGreases.
The myriad of bench oxidation tests that are now favored by many OEMs are definitely driving the antioxidant level upward. The formulator has to be able to exploit the synergies that exist between antioxidant components, Ogley agreed.
Brown added that the latest Volvo T-13 oxidation test is also driving antioxidancy requirements higher for heavy duty diesel lubricants.
Chemical restrictions are also behind a move to supplementary antiwear components, although new chemistry has been elusive without adding either sulfur or phosphorus. Brown said that boron-containing compounds have been widely tested, but sensitivity to water is a concern.
Other supplementary antiwear components that could replace ZDDP are extremely expensive and not as efficient, Ogley said. Development work in this area is still required as the push to thinner viscosity grades continues.
Friction modifiers, which lower metal-to-metal friction, are a clear growth area in the constant drive for improved fuel economy, but this growth is restricted by certain chemical disadvantages.
Historically, cost-effective, organic-based products have been used, for example glycerol monooleate.
There is a clear challenge to improve fuel economy whilst maintaining durability. Changes in test driving cycles more towards real world measurements may also have an impact on formulation needs, Brown said.
Researchers have aimed to find other materials, including those with greater friction-reduction life. Breakthroughs have proven difficult to achieve. Other good friction-reducing materials have been identified, but avoiding other debits, such as seal compatibility or reducing deposits, has been challenging.
Molybdenum compounds have also been widely used and are favored by Japanese OEMs. They are effective friction modifiers and antioxidants. However, they contain sulfur so treat rates are restricted by chemical limits and possible other downside such as corrosion.
Spinners and Losers
Absolute demand for crankcase additives remains a function of market dynamics, with most analysts predicting growth in Asia, especially China, with Europe and North America remaining static. Older technologies continue to be required as newer formulations are introduced at differing rates. Within this picture, the relative fortunes of component types will vary.
Demand for supplementary antioxidants is likely to grow in future, as thermal loadings on engines increase and chemical limits restrict the treat rates of existing ZDDP technology. Friction modifiers are also set to grow with a challenge to find newer materials with longer fuel economy durability.
Dispersant demand is anticipated to be stable. But the challenge is to create products with improved formulation viscometrics to support fuel economy benefits.
Metallic overbased detergents are anticipated to see reduced demand sometime after 2020 as basicity and sulfated ash of formulations tend to be lowered. Within this is a move in passenger cars towards more magnesium and less calcium-based formulations.
New component innovation is always important and will continue to challenge the industry’s chemists and engineers in the years ahead.
Philip Reeve is a chemist with 40 years of experience in the global lubricants and additive industry. He’s held positions at Afton, Infineum and ExxonMobil and is now a director of ADLU Consultancy.