Clean and Green: Developments in Environmentally-Friendly Lubricants Dr. Alan C. Eachus Villa Park, Illinois USA 12 th Annual Green Chemistry and Engineering Conference 25 June 2008 Washington, D.C.

2 Lubricant Consumption Data Lubricant Consumption (2006): 29.6% North & Latin America; 24.7% W. Europe; 45.9% Asia-Pacific & Rest of the World U.S. (2006) 2.45 billion U.S. gallons, total; ~44% = industrial, ~56% = automotive (2010) 2.86 billion gallons, (forecast) EU (2005) 4.5 million metric tons total; 2.4 million for vehicles Germany (annually) ~1.2 million metric tons 65-85% used or recycled;~200,000 tons lost to the environment

3 Desired Lubricant Attributes Low Coefficient of Friction (Lubricity) Low Pour Point (Good Low-Temperature Flow) High Viscosity Index (Less Change With Temperature) Thermal Stability Oxidative Stability Hydrolytic Stability Homogeneous (Complete Additive Solubilization) Compatible With Elastomers (Materials for Seals) Non-Volatile (Not Lost Through Evaporation) Power Transmission (In Hydraulic Fluids)

4 Lubricant-Ingredient Functions Base Fluid: 75 – 95% (lubricant/carrier) Additives: 5-25% Friction Modifiers (lower the coefficient of friction) Anti-Wear Additives (prevent metal-to-metal contact) Corrosion Inhibitors (provide protection for metals) Antioxidants (prevent degradation of lubricant) Viscosity-Index Modifiers (less thinning with heat) Pour-Point Depressants (aid low-temperature flow) Seal-Swell Agents (shrunken seals cause leaks) Defoamers/Antifoams (prevent entrained air) Detergents/Dispersants (prevent sludge in motor oils) Thickeners (in greases)

5 Descriptive Terminology Environmentally- Acceptable Aware Benign Compatible Friendly Preferable Responsible Safe Sensitive Suitable Biogenic Lubricants Bio-based Lubricants Bio-lubricants Renewable Lubricants “Green” Lubricants

6 Degrees of Biodegradability Ready Biodegradability (OECD 301 series) (an arbitrary classification, assumes eventual biodegradation after passing certain specified stringent tests) Inherent Biodegradability (OECD 302 series) ( unequivocal evidence, but may be longer than 28 days) Ultimate Biodegradability (OECD 302B/C) (complete, total mineralization) Primary Biodegradability (CEC L-33-A-94) (partial, first step in overall biodegradation, 21 days)

7 “Environmentally-Friendly” Criteria Biodegradability (60-70% decomposition by microbes in 3 – 4 weeks?) Aquatic Toxicity (adverse impact on algae, Daphnia and fish?) Renewability (derived from plant or animal sources?) Sustainability (total net impact on society over product lifetime?)

8 Especially-Sensitive Applications Total-Loss Lubricants: Chainsaw Oils Concrete Mold-Release Agents Outboard-Marine Engine Oils Railway-Track Greases Direct Environmental-Contact Potential: Agricultural- and Forestry-Machinery Lubricants Earthmoving and Construction Equipment Waterway Machinery Mining Lubricants and Hydraulic Fluids Submersible Pumps

9 Mineral Oil Complex hydrocarbon mixture Least-expensive base fluid Stable to oxidation and hydrolysis Compatible with current seals Relatively low viscosity index and high coefficient of friction (compared to other candidate base fluids) Volatile components are lost over time (lower flash point, viscosity increases, atmospheric emissions) Not considered environmentally-friendly, will biodegrade in ca. 3 years, depending on concentration

10 Polyalphaolefins (PAOs) Olefin oligomers made from linear monomers Good thermal and oxidation stability Relatively high viscosity index Compatible with other base fluids Good low-temperature flow Limited solubility for many additives May cause seal shrinkage Not renewably-sourced

11 Polyalkylene Glycols (PAGs) Random co-polymers of EO and PO Can be tailored: more EO and shorter chains induce more water-solubility & biodegradability High viscosity index, low volatility & pour point Good anti-wear properties and thermal stability Detergent properties, not sludge-forming Incompatible with paints and some seals Hydrophilic nature can lead to corrosion & foam Not renewably-sourced

12 Vegetable Oils Excellent lubricity, some anti-wear High viscosity index & low volatility Compatible with other base fluids & seals Good additive & contaminant solubilization Poor low-temperature fluidity Poor hydrolytic, thermal & oxidative stability Excellent biodegradability & renewability Less-stringent clean-up requirements if spilled

13 General Triglyceride Structure CH 2 OR 1 | HCOR 2 | CH 2 OR 3

14 Most-Common Triglyceride Fatty Acids Triacylglycerol Products Simple or Mixed Palmitic 16:0 Stearic 18:0 Oleic 18:1 Linoleic 18:2 Linolenic 18:3 Oleic is best compromise between oxidation resistance and low-temperature fluidity

15 Important Vegetable-Oil Sources Of Oleic Acid Soybean (Glycine max) South America, U.S., Australia Rapeseed/Canola (Brassica napus) Europe, China, Canada Sunflower (Helianthus annuus) C.I.S., Europe, Argentina Palm (Elaeis guineensis) Malaysia, Indonesia, Africa Safflower (Carthamus tinctorius) India, U.S., Mexico Other Sources: Olive, Cottonseed, Tallow.

16 Esters Made from alcohols and renewable fatty acids Very good lubricity, good viscosity index and high-temperature stability Can tailor performance properties and environmental features by choice of reactants Polyol esters are more hydrolysis-resistant than are diesters (from diols) Complex esters have better low-temperature fluidity & oxidative stability

17 Polyol Structures (No Beta-Hydrogens) CH 2 OH CH 2 OH | | CH 3 -C-CH 3 HOCH 2 -C-CH 2 OH | | CH 2 OH CH 2 OH Neopentyl Glycol (NPG) Pentaerythritol (PE) CH 2 OH | CH 3 CH 2 -C-CH 2 OH | CH 2 OH Trimethylolpropane (TMP)

18 Considerations in Complex-Ester Creation Longer acid chains lead to higher viscosity and VI, but also higher pour point Use at least one polyol among the alcohol reactants Linear carbon chains will add biodegradability but increase viscosity at -25°C Multiple and branched carbon chains will lower viscosity and pour point Use some carbon chains lower than C-10 for better oxidation resistance Smaller carbon chains can lead to lower flash point and greater toxicity Minimize steric hindrance around ester bond to maximize biodegradability Less symmetry in a molecule yields less opportunity for crystallization

19 General Lubricant Properties/Biodegradability Linear carbon chains degraded more rapidly (PAOs easier than mineral oil) Longer chains degraded more slowly Ester degradation is aided by hydrolysis More-viscous materials degraded more slowly Greater water-solubility assists degradation (PAGs with lower PO content degraded easier) (

20 Lubricant-Additive Chemical Classes Friction Modifiers: Fatty Acids/Esters; Triglycerides Corrosion Inhibitors: Succinimides; Organo-P/S cpds Antioxidants: Aromatic Amines; Hindered Phenolics; Cu, Sb or Zn Dialkyldithiophosphates or Carbamates Anti-Wear Additives: Metal Dithiophosphates Viscosity-Index Modifiers: Polyacrylmethacrylates; ά-olefin/ethylene or styrene/isoprene copolymers

21 Lubricant-Additive Chemical Classes Defoamers/Antifoams: Polysiloxanes Seal-Swell Agents: Aromatic Hydrocarbons Pour-Point Depressants: Polymethacrylates Detergents/Dispersants: PIBSA Derivatives; Ca/Mg Sulfonates or Salicylates Thickeners: Organoclays; Polyureas; Metal Soaps

22 OEM Requirements - Motor-Oil Response Longer-life emission systems - Low/no SAPS Better fuel economy – Lower viscosity, lower coefficient of friction Extended oil-drain intervals – Increased additive levels, more-effective additives, better- quality base stocks

23 A Final Thought The water, the soil and the air are not given to us by our parents, rather they are loaned to us by our children.