Comparing Conventional PAGs to Oil Soluble Polyalkylene Glycols L. W. Budd Lee The Dow Chemical Company Midland MI USA STLE, Detroit May 9 th 2013
Contents Background of Conventional PAGs Chemistry & physical properties Performance properties & functional benefits Oil Soluble PAGs Physical properties and functional properties Comparison of properties to conventional PAGs Practical Applications for OSPs Deposit control of hydrocarbon oils Friction reduction of hydrocarbon oils Improving the hydrolytic stability of vegetable oils and esters Corrosion inhibitor boosters Summary
Presentation Objectives To give an overview of oil soluble PAGs a new type of Group V base oil and performance additive To explain their differences from conventional PAGs To highlight some practical ways to use OSPs in modern lubricant formulations that are difficult or impossible with conventional PAGs
Conventional Polyalkylene Glycol Technology Typical Synthesis Route to Polyalkylene Glycols Initiator (ROH) catalyst + +/or PAG ethylene oxide (EO) propylene oxide (PO) High performance synthetic lubricants Solve problems that mineral oils cannot Synthesized from ethylene oxide and propylene oxide Flexible chemistry polymers can be tailor designed to meet many requirements Extensively researched over 60 years Types of PAGs by chemical family Homo-polymers of EO Homo-polymers of PO Block copolymers of EO/PO Reverse block copolymers of EO/PO Random copolymers of EO/PO PAGs can be designed to have a wide range of molecular weights, viscosities and functional performance
Applications for PAGs Established Applications of PAGs Air Compressor Fluids Natural Gas Compressor Fluids Water Glycol Hydraulic Fluids Metalworking Fluids Quenchants Gear Oils Recent New Applications for PAGs Gas Turbine Oils Wind Turbine Lubricants Non-Sheening Hydraulic Fluids
Attributes of Conventional PAGs Elastomer compatibility Generally preferred Friction control Viscosity index Pour points Biodegradability Key Typical Features High V.I.s (up to 400) Pour points to -45 o C Bio-degradability (10-90%) Mild anti-wear Excellent deposit control Excellent friction control Hydrolytically stable Low heats of combustion Oxidation stability Deposit control Antiwear Hydrolytic stability Perceived Disadvantages Oil miscibility Some elastomer incompatibility Hygroscopicity Oil miscibility By re-engineering the polymer architecture it is possible to design OIL SOLUBLE PAGs and retain many of the features of conventional PAGs but improve their perceived disadvantages
Water Soluble, Water Insoluble and Oil Soluble PAGs Simplistic schematic of the types of oxides used in designing PAGs Homo-polymers or Copolymers (random and block) are often used for conventional lubricants Oil soluble PAGs derived from higher oxides have been researched in the past. New OSPs are derived from butylene oxide as one of the commercially available building blocks Oil soluble PAGs are new and build on 60 years of experience in using PAGs across many lubrication industries
Attributes of OSPs versus Traditional PAGs Viscosity index Friction control Pour points Elastomer compatibility Oxidation stability Biodegradability Antiwear OSP PAG Deposit control Hydrolytic stability Oil miscibility Oil Soluble PAGs offer formulators greater flexibility, especially as performance additives in hydrocarbon lubricants
New Oil Soluble PAGs Typical Properties Polymers derived from downstream derivatives of butylene oxide KV40 cst KV100 cst Viscosity Index Pour Point oc Flash Point, oc Aniline Point, oc ASTM D445 ASTM D445 ASTM D2270 ASTM D97 ASTM D92 ASTM D611-01 OSP-A 18 4 123-41 204 n/d OSP-B 32 6.5 146-57 216 <-30 OSP-C 46 8.5 164-57 210 <-30 OSP-D 68 12 171-53 218 <-30 OSP-E 150 23 186-37 228 <-30 OSP-F 220 32 196-34 226-22 OSP-G 320 36 163-37 230 <-30 OSP-H 460 52 177-35 235 <-30 OSP-I 680 77 196-30 243 <-30
Property Comparison For Two ISO Grades Property Method EO/PO-32 PO-32 OSP-32 EO/PO-46 PO-46 OSP-46 Kinematic Viscosity at 40 C ASTM D445 32 32 32 46 46 46 Kinematic Viscosity at 100 C ASTM D445 7 7 6.4 10.5 9 8.5 Viscosity Index ASTM D445 190 185 146 210 190 164 Pour Point, C ASTM D97-42 -41-57 -40-40 -57 Specific Gravity, 20/20 C ASTM D1298 1.028 0.985 0.942 1.036 0.985 0.949 Flashpoint, C ASTM D92 205 215 216 230 215 210 Oil soluble PAGs have lower VI, but improved pour points
Oxidation Performance of PAGs and OSPs 1200 RPVOT ASTM D2272 30 ASTM D2893B 121 o C, 312 hours 1000 25 RPVOT, mins 800 600 400 200 % viscosity change 20 15 10 5 Onset temp. Degradation, oc 0 250 200 150 100 50 0 EO/PO OSP EO/PO + 2% AO OSP + 2% AO Thermo-gravimetric Analysis Heating rate 10 o C/min, in air Onset temp = 2% weight loss EO/PO OSP EO/PO + 2% AO OSP + 2% AO 0 EO/PO OSP EO/PO + 2% AO OSP +2% AO AO = alkylated diphenylamine EO/PO is ISOVG-46 PAG base oil Oxidation performance indicates: Similar performance to conventional EO/PO PAGs Good response to conventional aminic anti-oxidants
Hygroscopicity of PAGs Hygroscopicity of ISO-VG46 PAG base oil chemistries 6 Relative humidity 80% and temperature 50oC % Water absorption 5 4 3 2 1 0 EO/PO PO OSP-46 Water absorbing characteristics lower for OSPs than traditional PAGs PAGs act as polymeric sponges binding water within the structures (water is not free at levels of several thousand ppm)
Practical Examples of Using OSPs Several examples will be highlighted and performance aspects compared to some existing technologies Deposit control in hydrocarbon oils Friction control in hydrocarbon oils Hydrolytic stability additive in esters Solubility and seal swell additive
Deposit Control PAO Compressor Oil (ISO-68) Oxidation test Modified ASTM D-2893B (72 hours at 60 o C then 72 hours at 150 o C and the cycle repeated for 30 days) KV 40 change = 10.1% TAN change = 0.1 mg KOH/g Visual: significant deposits 7 days 14 days 21 days 30 days initial Fully Synthetic OSP Compressor Oil (ISO-68) KV 40 change = 4.0% TAN change = 0.3 mg KOH/g Visual: No deposits and translucent 7 days 14 days 21 days 30initial days
OSP as Deposit Control Additives Group I Mineral Oil Deposits Group I Mineral oil + Synthetic Ester (10%) Deposits Group I Mineral Oil + Alkylated Naphthalene (10%) Deposits initial 50 days initial 41 days initial 41 days Group I Mineral Oil + OSP-C (10%) Group I Mineral Oil + OSP-C (5%) Group I Mineral Oil + OSP-C (1%) Minor deposit initial 50 days initial 50 days initial 50 days Modified ASTM D2893B at 121 o C and extended time
Deposit Control Features of OSPs in Hydrocarbon Oils Group I Oil Group I Oil + 10% OSP-C Inclusion of an OSP improves deposit control in a Group I mineral oil 0 days 50 days 0 days 50 days Group II Oil Group II Oil + 10% OSP-C Inclusion of an OSP improves deposit control in a Group II mineral oil 0 days 70 days 0 days 70 days Modified ASTM D2893B (extended test) temperature is 121 o C. Inclusion of an OSP improves deposit control
Deposit Control and Formulated Compressor Fluids Group II compressor oil aged over 60 days at 121 o C using modified ASTM D2893B Oxidation by-products of hydrocarbon oils An example of degradation pathway Deposits evidence of deposits clear and translucent Probable explanation is polar oxidation by-products are soluble in the polar OSP co-base oil
Deposit Control in Environmentally Friendly Natural Ester based Hydraulic Fluids using OSPs Vegetable oil Deposits Vegetable oil + 10% OSP-C Minor deposits Accelerated oxidation test using modified ASTM D2893B at 121 o C for 72 hours Visual inspection of the tubes shows evidence for better deposit control and improved fluid cleanliness Hypothesis is that OSP is solubilizing the oxidation by-products of natural esters initial 72 hours initial 72 hours Conceptually it is possible to extend fluid life using OSPs as additives or co-base oils in vegetable oils
Friction Performance of OSPs as Additives in PAO 0.4 Mini-traction machine, steel ball on steel disc, temperature 80 o C, speed 15 mm/sec, Slide roll ratio = 10%, Pressure = 0.9GPa Friction Coefficient 0.35 0.3 0.25 0.2 0.15 0.1 0.05 PAO PAO + 10% OSP PAO + 5% OSP 0 0 500 1000 1500 2000 Time (s) Polyalphaolefin is a PAO-8 base oil (un-additized) OSPs showed film forming behavior in initial tribology evaluations
Friction Control of OSPs in a Group III Base Oil 0.14 Mini-traction machine, steel ball on steel disc, temperature 80 o C, slide roll ratio = 50%, load = 50N 0.12 GpIII Friction coefficient 0.1 0.08 0.06 0.04 GpIII + 1% OSP GpIII + 5% OSP 0.02 0 1 10 100 1000 10000 Log [speed]
Friction Control of OSPs in a PAO-4 Base Oil 0.2 0.18 Mini-Traction Machine, steel ball on steel disc, temperature 80 o C, slide roll ratio = 50%, load = 50N Friction coefficient 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 PAO-4 PAO-4 + 1% OSP 0 1 10 100 1000 Log [speed] Evidence of friction control behavior in Group III and IV hydrocarbons
OSPs as Additives in Ester Based Environmentally Friendly Hydraulic Fluids Vegetable based hydraulic fluids (HETG) Excellent wear performance Biodegradable and renewable High viscosity indices Synthetic esters (HEES) also used in more demanding applications Good oxidation stability Good low temperature properties Excellent wear characteristics Some are biodegradable and renewable Limitations of Esters Natural and synthetic esters can be prone to hydrolysis Impact can be a shorter fluid life and higher risk of equipment damage
OSPs and Hydrolytic Stability Improvements of Esters Hydrolytic stability: Modified ASTM D2619 extended time Vegetable Oil Vegetable Oil + 10% OSP-C Synthetic Polyol ester Synthetic polyol ester + 10% OSP-C KV 40 mm 2 /sec 32 34.5 22.9 23.9 Viscosity index 225 220 144 151 TAN change mg KOH/g 0.4 0.1 0.07 0.05 Total acidity of water layer mg KOH/g 7.3 1.2 3.2 1.2 Copper appearance 3a 1b 2c 1b KV 40 change % +4.0 + 4.0-4.9 0.9 OSP appears to act as a polymeric sponge for water rendering it less active
Comparison of a Diester and an OSP as Seal Swell Additives Adipate esters are common seal swell additives KV40, mm 2 /sec KV100, mm 2 /sec Viscosity index Pour Point, o C OSP-B offers similar viscometric properties Adipate diester 28.0 5.2 135-54 OSP-B 32.0 6.5 146-57 35 NBR volume swell of base oils 168 hours at 100 o C 4 NBR volume swell of formulated blends for 168 hours at 100 o C Volume change, % 30 25 20 15 10 Volume change, % 2 0-2 -4 PAO + 20% adipate ester PAO + 20% OSP-B 5 0 Adipate diester OSP-B -6-8 PAO PAO is a blend of PAO-40 and PAO-8 to make a ISO-320 fluid OSP-B provides an alternative option to diesters but offers improved hydrolytic stability
PAG Industrial Gear Lubricants and OSP Corrosion Inhibitor Boosters PAGs in Industrial Gear Oils (worm gears) ISOVG-150 to 1000 Significantly higher energy efficiency advantages than hydrocarbon oils Lower operating oil temperatures Find use in food grade approved lubricants PAGs in Wind Turbine Lubricants ISO-VG320 Can form thick EHD films under high contact pressures Clean and deposit free Long fluid change intervals Most commercially available PAG gear lubricants are derived from EO/PO polymers but fail to meet the ASTM D665B corrosion test (synthetic sea water test)
OSPs as Corrosion Inhibitor Boosters in PAGs ISO-320 PAG Gear Oil Chemistry % % Base Oil (ISO-320) PAG (EO/PO) 97.0 92.0 Additive package AO/EP/AW 2.5 2.5 Corrosion inhibitor Imidazoline 0.5 0.5 Corrosion inhibitor booster OSP ASTM D665A / D665B No booster With booster 5 Pass/Fail Pass/Pass Deionised Water Synthetic Sea Water Deionised Water Synthetic Sea Water ISO-68 PAG Compressor Oil Chemistry % % 97.75 92.75 Base Oil (ISO-68) PAG (EO/PO) Additive package AO/AW 2.0 2.0 Corrosion inhibitor Amine phosphate 0.25 0.25 Corrosion inhibitor booster OSP ASTM D665A / D665B No booster With booster 5 Pass/Fail Pass/Pass Deionised Water Synthetic Sea Water Deionised Water Synthetic Sea Water
SUMMARY Oil Soluble PAGs (OSP) are a new and versatile Group V base oil and performance additive Some practical benefits in lubricant formulations include: Deposit control in hydrocarbon oils for turbine, compressor and hydraulic oils Friction control for gear oils and engine oils Hydrolytic stability improvers for natural esters Seal swell additives Corrosion inhibitor boosters in PAGs OSPs provide our industry with another tool for solving modern tribology and equipment challenges
Thank you! For further questions or assistance please contact L. W. Budd Lee Technical Service Manager Ph: 989-636-1415 Email: LWLee@dow.com Or see www.dowosp.com Martin R. Greaves Research Leader Ph+41 447282071 mrgreaves@dow.com