Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M135/00—Lubricating compositions characterised by the additive being an organic non-macromolecular compound containing sulfur, selenium or tellurium
  • C10M135/08—Lubricating compositions characterised by the additive being an organic non-macromolecular compound containing sulfur, selenium or tellurium containing a sulfur-to-oxygen bond
  • C10M135/10—Sulfonic acids or derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M165/00—Lubricating compositions characterised by the additive being a mixture of a macromolecular compound and a compound of unknown or incompletely defined constitution, each of these compounds being essential
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2205/00—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions
  • C10M2205/02—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions containing acyclic monomers
  • C10M2205/028—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions containing acyclic monomers containing aliphatic monomers having more than four carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2205/00—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions
  • C10M2205/02—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions containing acyclic monomers
  • C10M2205/028—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions containing acyclic monomers containing aliphatic monomers having more than four carbon atoms
  • C10M2205/0285—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions containing acyclic monomers containing aliphatic monomers having more than four carbon atoms used as base material
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/10—Carboxylix acids; Neutral salts thereof
  • C10M2207/12—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms
  • C10M2207/121—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of seven or less carbon atoms
  • C10M2207/124—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of seven or less carbon atoms containing hydroxy groups; Ethers thereof
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/26—Overbased carboxylic acid salts
  • C10M2207/262—Overbased carboxylic acid salts derived from hydroxy substituted aromatic acids, e.g. salicylates
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
  • C10M2219/04—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions containing sulfur-to-oxygen bonds, i.e. sulfones, sulfoxides
  • C10M2219/044—Sulfonic acids, Derivatives thereof, e.g. neutral salts
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
  • C10M2219/04—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions containing sulfur-to-oxygen bonds, i.e. sulfones, sulfoxides
  • C10M2219/046—Overbased sulfonic acid salts
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/54—Fuel economy
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/04—Oil-bath; Gear-boxes; Automatic transmissions; Traction drives

Definitions

• the present invention provides transmission fluid compositions having improved power transmission properties through the presence therein of certain defined additives.
• the invention provides transmission fluid compositions for automotive vehicles, the use of which demonstrably increase the fuel efficiency of the vehicle during operation.
• the invention further provides a process for the manufacture of such transmission fluid compositions, a method of improving the energy efficiency of a transmission, and an additive concentrate for a transmission fluid, and other aspects as hereinafter described.
• the present invention concerns transmission fluid compositions having improved power transmission properties through the presence therein of certain defined additives.
• the invention provides transmission fluids for automotive vehicles, the use of which demonstrably increase the fuel efficiency of the vehicle during operation.
• the present invention has determined that a class of polyalphaolefin polymer made by a particular form of polymerisation reaction has utility as a performance-enhancing additive for transmission fluids, when present in conjunction with one or more viscosity modifiers and specific detergent compounds, wherein the combination functions to improve the power transmission properties of the fluid.
• This combination of additives enables the transmission to operate with greater energy efficiency, as demonstrated for example by an increase in the fuel efficiency of the vehicle during operation.
• the polyalphaolefin shows advantageous performance as an additive for this purpose when used in an amount that does not exceed 4 percent by weight of the total transmission fluid composition, and optimal performance when used in an amount in the range of 1 to 3 percent by weight of the total transmission fluid composition.
• US-A-2010/0035778 provides a composition for a power transmitting fluid that has inter alia improved fuel economy which preferably comprises an additive and a base stock having a polyalphaolefin blend.
• the additive preferably includes inter alia a viscosity index improver.
• This teaching reports the use of a basestock that includes a polyalphaolefin (PAO) or PAO blend that has an unconventional viscosity profile, and recites a fluid composition having from about 8% to about 90% by weight of the PAO blend.
• PAO polyalphaolefin
• the worked example of the composition contains 77.4% by weight of the PAO blend, being comprised of PAO 2cSt and PAO 6 cSt in proportions of 9.4% and 68.0% by weight respectively, along with a viscosity modifier and detergent additive.
• PAO blend being comprised of PAO 2cSt and PAO 6 cSt in proportions of 9.4% and 68.0% by weight respectively, along with a viscosity modifier and detergent additive.
• any number of PAOs may be employed so long as the PAO blend is selected such that the base viscosity of the fluid is greater than or equal to 4.0cSt at 100°C.
• This teaching fails to conceptually recognise the benefit arising from use of a specific polyalphaolefin at additive treat levels within the transmission fluid, and again focusses on altered bulk viscometrics as the means by which fluid performance is enhanced.
• each alkaline earth metal detergent compound present in the transmission fluid composition is a neutral or overbased calcium salicylate compound, and more preferably the total amount of these calcium salicylate compound(s) is such as to provide the transmission fluid composition with a calcium content of between 50 and 250 parts per million by weight, per weight of the transmission fluid composition.
• the present invention has found that the nature of the viscosity modifier used in combination with the defined polyalphaolefin influences the optimal degree of improvement in energy efficiency achieved through use of the resulting transition fluid composition, and in particular the degree of improvement in fuel efficiency of the vehicle.
• different viscosity modifiers demonstrate differential improvements in combination with the polyalphaolefin when compared in formulated oils having equivalent viscometric properties. This further improvement in efficiency is therefore attributable to the nature of the viscosity modifier per se rather than to differential viscosity modification effects.
• the present invention provides a transmission fluid composition consisting of:
• The, or each, polyalphaolefin compound (iii) is made by a polymerisation reaction in which the corresponding alphaolefin feedstock is polymerised through the action of a metallocene catalyst.
• a metallocene catalyst Such polyalphaolefins are known per se, and are sometimes referred to in the polymer art as "mPAO". They possess a structure different from polyalphaolefins derived from other catalytic processes.
• the action of the metallocene catalyst is such as to cause the formation of a polymer product having a narrow molecular weight distribution, and a structure that embodies a high proportion of head-to-tail monomer unit additions, i. e. can be regarded as an essentially ideal polymer.
• the literature for such materials also reports a more ordered pattern of hydrocarbon side chains with fewer short side chains than other processes. The result is a polymer with a more "perfect" structure and different properties.
• the present invention has determined that such polyalphaolefins show a particular benefit when used as performance-enhancing additives in transmission fluid compositions.
• the additive benefit from such polyalphaolefins is seen at a treat rate of not more than 4 percent by weight of the total transmission fluid composition, preferably between 1 and 3 percent by weight, and optimally between 2 and 3 percent by weight.
• Such treat rates correspond to typical additive treat rates in such fluids, and are not to be confused with the use of synthetic polymers as lubricating oils per se (sometimes called "basestocks") or as basestock blending components, which involve the incorporation of larger relative quantities of polymer for constituting the bulk volume of base lubricating oil.
• the present invention provides a process for the manufacture of a transmission fluid composition, the composition consisting of:
• the process of the present invention is employed to manufacture an automotive transmission fluid, and in particular wherein the additions in step b) improve the efficiency of power transmission provided by the resulting composition when used in the vehicle, as demonstrated by an increase in the fuel efficiency of the vehicle during operation.
• the present invention provides a method of improving the energy efficiency of a transmission, comprising the use therein of the transmission fluid composition defined in the first aspect or of the transmission fluid composition obtained by the process of the second aspect.
• the transmission is preferably a transmission for an automotive vehicle, and the improvement in energy efficiency is preferably an increase in fuel economy of the vehicle during operation.
• the invention provides an additive concentrate for a transmission fluid, the concentrate consisting of a suitable carrier liquid, (ii) a viscosity modifier or blend of viscosity modifiers, and (iii) a polyalphaolefin compound or mixture of polyalphaolefin compounds made by the metallocene-catalysed polymerisation of an alphaolefin feedstock, and (iv) one or more detergent additives, at least one of which comprises one or more alkaline earth metal detergent compounds wherein at least one alkaline earth metal detergent compound is an alkaline earth metal salicylate or sulphonate compound.
• the total amount of polyalphaolefin compound(s) (iii) present in the concentrate is such that, after addition of the concentrate at its specified treat rate to the transmission fluid, said compounds (iii) constitute no more than 4 percent by weight of the resulting transmission fluid composition.
• the transmission fluid composition consists of four essential elements (i), (ii), (iii) and (iv).
• the components are :
• the total amount of the polyalphaolefin compound(s) (iii) in the transmission fluid composition does not exceed 4 percent by weight of the composition, regardless of the means of incorporation.
• some, or all, of the small amount of polyalphaolefin(s) (iii) in the composition of the first aspect may be introduced to the composition via incorporation in the lubricating oil or oil blend (i).
• the lubricating oil or oil blend component (i) per se contains no such polyalphaolefins (iii), and that these essential compounds (iii) are instead incorporated into the composition by direct addition as a discrete additive in the process of manufacture of the composition, or are mixed with the viscosity modifier additive or blend of viscosity modifier additives (ii) to form a single additive concentrate prior to their addition to the lubricating oil or blend of oils.
• the polyalphaolefin compound(s) (iii) may be mixed with one or more of the detergent additive (iv) to form a single additive concentrate prior to addition to the lubricating oil or blend of oils.
• the lubricating oil or oil blend (i) constitutes the bulk of the fluid composition.
• Oils useful in this invention as the lubricating oil, or for constituting the oil blend are derived from natural lubricating oils, synthetic lubricating oils, and mixtures thereof.
• both the natural and synthetic lubricating oil will each have a kinematic viscosity ranging from about 1 to about 100 mm 2 /s (cSt) at 100°C depending on the specification or quality of transmission fluid sought, although typical applications will require each oil to have a viscosity ranging from about 2 to about 8 mm 2 /s (cSt) at 100°C.
• Natural lubricating oils include animal oils, vegetable oils (e.g., castor oil and lard oil), petroleum oils, mineral oils, and oils derived from coal or shale.
• the preferred natural lubricating oil is mineral oil.
• Suitable mineral oils include all common mineral oil basestocks. This includes oils that are naphthenic or paraffinic in chemical structure. Oils that are refined by conventional methodology using acid, alkali, and clay or other agents such as aluminum chloride, or they may be extracted oils produced, for example, by solvent extraction with solvents such as phenol, sulfur dioxide, furfural, dichlordiethyl ether, etc. They may be hydrotreated or hydrofined, dewaxed by chilling or catalytic dewaxing processes, or hydrocracked. The mineral oil may be produced from natural crude sources or be composed of isomerized wax materials or residues of other refining processes.
• the mineral oils will have kinematic viscosities of from 2.0 mm 2 /s (cSt) to 10.0 mm 2 /s (cSt) at 100°C.
• the preferred mineral oils have kinematic viscosities of from 2 to 8 mm 2 /s (cSt), and most preferred are those mineral oils with viscosities of 3 to 6 mm 2 /s (cSt) at 100°C.
• Synthetic lubricating oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as oligomerized, polymerized, and interpolymerized olefins [e.g., polybutylenes, polypropylenes, propylene, isobutylene copolymers, chlorinated polylactenes, poly(1-hexenes), poly(1-octenes), poly-(1-decenes), etc., and mixtures thereof]; alkylbenzenes [e.g., dodecyl-benzenes, tetradecylbenzenes, dinonyl-benzenes, di(2-ethylhexyl)benzene, etc.]; polyphenyls [e.g., biphenyls, terphenyls, alkylated polyphenyls, etc.]; and alkylated diphenyl ethers, alkylated diphenyl sulf
• the preferred oils from this class of synthetic oils are Group IV basestocks, i.e. polyalphaolefins (PAO), including hydrogenated oligomers of an alpha-olefin, particularly oligomers of 1-decene, especially those produced by free radical processes, Ziegler catalysis, or cationic, Friedel-Crafts catalysis.
• PAO polyalphaolefins
• the polyalphaolefins typically have viscosities in the range of 2 to 20 cSt at 100°C, preferably 4 to 8 cSt at 100°C. They may, for example, be oligomers of branched or straight chain alpha-olefins having from 2 to 16 carbon atoms, specific examples being polypropenes, polyisobutenes, poly-1-butenes, poly-1-hexenes, poly-1-octenes and poly-1-decene. Included are homopolymers, interpolymers and mixtures.
• the lubricating oil or lubricating oil blend (i) be additionally constituted from any polyalphaolefin (iii), i.e. mPAO made by the metallocene-catalysed polymerisation of an alphaolefin feedstock, it is important that such polyalphaolefins (iii) do not collectively contribute more than 4% by weight of the total transmission fluid composition.
• any and all polyalphaolefin(s) constituting the lubricating oil or lubricating oil blend (i) are not made by the metallocene-catalysed polymerisation of an alphaolefin feedstock.
• Synthetic lubricating oils also include alkylene oxide polymers, interpolymers, copolymers, and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, etc.
• This class of synthetic oils is exemplified by: polyoxyalkylene polymers prepared by polymerization of ethylene oxide or propylene oxide; the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g., methyl-polyisopropylene glycol ether having an average molecular weight of 1000, diphenyl ether of polypropylene glycol having a molecular weight of 1000 - 1500); and mono- and poly-carboxylic esters thereof (e.g., the acetic acid esters, mixed C 3 -C 8 fatty acid esters, and C 12 oxo acid diester of tetraethylene glycol).
• Another suitable class of synthetic lubricating oils comprises the esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebasic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkylmalonic acids, alkenyl malonic acids, etc.) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoethers, propylene glycol, etc.).
• dicarboxylic acids e.g., phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebasic acid, fumaric acid, adipic
• esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and the complex ester formed by reacting one mole of sebasic acid with two moles of tetraethylene glycol and two moles of 2-ethyl-hexanoic acid, and the like.
• a preferred type of oil from this class of synthetic oils is adipates of C 4 to C 12 alcohols.
• Esters useful as synthetic lubricating oils also include those made from C 5 to C 12 monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylolpropane pentaerythritol, dipentaerythritol, tripentaerythritol, and the like.
• the lubricating oils may be derived from refined, rerefined oils, or mixtures thereof.
• Unrefined oils are obtained directly from a natural source or synthetic source (e.g., coal, shale, or tar sands bitumen) without further purification or treatment.
• Examples of unrefined oils include a shale oil obtained directly from a retorting operation, a petroleum oil obtained directly from distillation, or an ester oil obtained directly from an esterification process, each of which is then used without further treatment.
• Refined oils are similar to the unrefined oils except that refined oils have been treated in one or more purification steps to improve one or more properties.
• Suitable purification techniques include distillation, hydrotreating, dewaxing, solvent extraction, acid or base extraction, filtration, and percolation, all of which are known to those skilled in the art.
• Rerefined oils are obtained by treating used oils in processes similar to those used to obtain the refined oils. These rerefined oils are also known as reclaimed or reprocessed oils and are often additionally processed by techniques for removal of spent additives and oil breakdown products.
• Suitable lubricating oils are those basestocks produced from oligomerization of natural gas feed stocks or isomerization of waxes. These basestocks can be referred to in any number of ways but commonly they are known as Gas-to-Liquid (GTL) or Fischer-Tropsch base stocks.
• GTL Gas-to-Liquid
• Fischer-Tropsch base stocks Fischer-Tropsch base stocks
• the lubricating oil (i) may be a blend of one or more of the above described oils, and a blend of natural and synthetic lubricating oils (i.e., partially synthetic) is expressly contemplated under this invention.
• the viscosity modifier or blend of viscosity modifiers (ii) may be a single compound or a blend of compounds capable of modifying the viscosity of lubricating oil when added thereto, so as to make its viscosity profile more advantageous for lubricant function.
• lubricating oils experience a range of operating temperatures within the device being lubricated and, as viscosity is a temperature-dependent characteristic, must therefore maintain an appropriate viscosity throughout the range of operating temperatures, such that the oil neither becomes too viscous ('thick') at lower temperatures to cause viscous drag in the device, nor too thin to provide adequate lubrication at higher temperatures.
• Viscosity modifiers typically have the property of increasing the viscosity of the oil at higher temperatures, so offsetting the natural thinning of the lubricant base-stock, whilst having lesser (or no) thickening effect at lower temperatures, so as to not contribute substantially to viscous drag.
• preferred viscosity modifiers show a greater resistance to loss of activity over time, when exposed to the shear forces and other degrading effects that a lubricant experiences during the rigours of operation.
• the viscosity modifier or blend of viscosity modifiers suitable for use as component (ii) of the invention is thus, in its broadest aspect, any viscosity modifier capable of reducing the temperature-dependent variation in viscosity inherent in the lubricating oil (or blend of lubricating oils).
• certain classes of viscosity modifier are especially suitable in combination with components (i), (iii) and (iv) to provide transmission fluid compositions with the advantages of the present invention.
• the viscosity modifier or blend of viscosity modifiers (ii) is preferably a polymer or blend of polymers derived from one or more olefin or unsaturated ester monomers; and more preferably a polymer or blend of polymers derived from one or more olefin monomers, or from one or more ⁇ , ⁇ -unsaturated ester monomers such as alkyl acrylates and alkyl methacrylates, or from one or more olefins and one or more ⁇ , ⁇ -unsaturated ester monomers such as alkyl acrylates and alkyl methacrylates.
• the viscosity modifier or blend of viscosity modifiers (ii) is a polymer or blend of polymers selected from one or more of the following groups :
• Materials in group (ii)(a) are prepared by the polymerisation of one or more alkylacrylate or alkylmethacrylate monomers, wherein the alkyl groups preferably contain from 1 to 20, more preferably 1 to 10 carbon atoms, using techniques known in the art, such as radical polymerisation. Such materials are known in the art and are commercially available, an example being VISCOPLEX® 12-075 supplied by Evonik Rohmax USA, Inc.
• Materials in the group (ii)(b) are prepared by the stepwise polymerisation of a core portion from one or more alkylacrylate or alkylmethacrylate monomers, wherein the alkyl groups preferably contain from 1 to 30, more preferably 1 to 20 carbon atoms, followed by further polymerisation with such monomers to form the pendant arms.
• Suitable processes include atom transfer radical polymerisation (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerisation.
• the arms can be separately formed and attached to the core via reaction at the linking groups.
• Such materials are known in the art.
• comb is known in the polymer art, and refers to the comb-like architecture of the polymer which possesses a series of side-chains depending from the main backbone chain, these side-chains being formed either from the alkyl substituents of the alkyl acrylate or methacrylate monomer units, or from the residues of the olefin monomers, or both.
• the comb polymer (ii)(c) is prepared from one or more alkylacrylate or alkylmethacrylate monomers, it is formed by the polymerisation of one or more alkylacrylate or alkylmethacrylate monomers wherein the alkyl chains contain between 4 and 20 carbon atoms, preferably by radical polymerisation.
• the comb polymer (ii)(c) is prepared from one or more olefin or polyolefin monomers, it is formed by the polymerisation of one or more olefin monomers containing between 4 and 20, such as 4 to 12, carbon atoms. Alternatively, it may be prepared from one or more polyolefin macromonomers providing alkyl or alkenyl groups of considerable size, which form the side-chains of the resulting comb polymer structure.
• the comb polymer (ii)(c) is prepared by the copolymerisation of one or more alkylacrylate or alkylmethacrylate monomers with one or more olefin or polyolefin monomers.
• the backbone is formed by the co-polymerising (meth)acrylate and olefin or polyolefin monomer units, with the alkyl ester groups of the (meth)acrylate units and the residues of the olefin or polyolefin depending from the resulting backbone to form the comb structure.
• the alkyl groups of the alkylacrylate or alkylmethacrylate monomers preferably contain between 4 and 20, such as 8 to 18, carbon atoms; whilst the co-monomer is preferably an olefin or polyolefin providing a longer dependant chain to the resulting copolymer, such as a long chain alpha-olefin or a polyolefin macromonomer such as poly(isobutylene) or hydrogenated poly(butadiene).
• Further olefinically-unsaturated comonomers may be used in the preparation, for example styrene or ⁇ - ⁇ unsaturated esters.
• such polymers When present in the lubricating oil, such polymers are capable of significant expansion when energy is applied (such as occurs when the oil heats up during operation), and this thermal expansion behaviour enables them to entrain more oil within a fluid network of extended comb structures, and so oppose the thinning in oil viscosity that otherwise typically occurs with increasing temperature.
• energy such as occurs when the oil heats up during operation
• thermal expansion behaviour enables them to entrain more oil within a fluid network of extended comb structures, and so oppose the thinning in oil viscosity that otherwise typically occurs with increasing temperature.
• the polyalphaolefin compound or compounds (iii) are those by the metallocene-catalysed polymerisation of an alphaolefin feedstock.
• Such "mPAO" materials are known in the art per se and are described, for example, in US-A-2007/145924 along with their method of manufacture via metallocene catalysis. In this reference they are described as a lubricant base-stock component and used primarily to make high viscosity basestock blends.
• the polyalphaolefin compound(s) (iii) are used in additive quantities in the transmission fluid composition in combination with a viscosity modifier additive or blend of viscosity modifier additives (ii) and specific detergent additives(s) (iv) to improve the energy efficiency of a transmission utilising said fluid.
• Metallocene-made polyalphaolefins (iii) having characteristics particularly suitable for the practice of this invention can be produced from a feedstock containing one or more, preferably two or more, linear C 6 to C 18 alphaolefins.
• Preferred polyalphaolefins (iii) are those made from a feedstock mixture of C6 and C18 linear alphaolefins or a mixture of C 6 and C 12 alphaolefins.
• the feedstock is typically contacted with an activated metallocene catalyst under polymerisation conditions known in the art, to give the compounds (iii).
• the invention employs Spectrosyn EliteTM 150 as the polyalphaolefin (iii).
• This material is available as an item of commerce through the above source according to a published specification, and has a typical kinematic viscosity at 100°C of 156 mm 2 /s as measured by ASTM D445, and a typical viscosity index of 206 as measured by ASTM D2270, together with a pour point of minus 33°C as measured by ASTM D5950/D97.
• compositions of the invention may, via additive (iv), additionally contain other polyalphaolefins.
• the present invention concerns transmission fluid compositions having improved power transmission properties.
• Examples of other, less preferred types of power transmitting fluids included within the scope of this invention are gear oils, hydraulic fluids, tractor fluids, universal tractor fluids and the like.
• the invention provides transmission fluids for automotive vehicles, the use of which demonstrably increase the fuel efficiency of the vehicle during operation.
• the transmission fluid composition of the invention is preferably an automotive transmission fluid, such as an automatic transmission fluid (hereinafter referred to as "ATF”), continuously variable transmission fluid (“CVTFs”), or double clutch transmission fluid (“DCTFs").
• ATF automatic transmission fluid
• CVTFs continuously variable transmission fluid
• DCTFs double clutch transmission fluid
• detergent additive is used to denote an additive comprising one or more detergent compounds, and optionally other compounds ('components') which function as performance-enhancing additives for transmission fluids.
• detergent additives are sometimes generally known as detergent packages or detergent-inhibitor packages and may contain a variety of other components and a mutually-compatible solvent or dispersion medium.
• These other components include additional detergents, dispersants, antiwear agents, corrosion inhibitors, extreme pressure additives, and the like. They are typically disclosed in, for example, " Lubricant Additives” by C. V. Smallheer and R. Kennedy Smith, 1967, pp. 1-11 and U.S. Patent 4,105,571 .
• additive (iv) in an automotive transmission fluid Representative amounts of typical components of additive (iv) in an automotive transmission fluid are summarized as follows: Additive (Broad) Wt.% (Preferred) Wt.% Dispersants 0.10 - 10 2-5 Antiwear Agents 0.005 - 5 0.5 - 3 Friction modifiers 0.05 - 5 0.5 - 3.0 Corrosion Inhibitor 0.01 - 3 0.02 - 1 Antifoaming Agents 0.001 - 5 0.001 - 0.5 Pour Point Depressants 0.01 - 2 0.01 - 1.5 Seal Swellants 0.1- 8 0.5 - 5 Diluent Balance Balance Balance Balance
• At least one additive (iv) comprises one or more alkaline earth metal detergent compounds wherein at least one alkaline earth metal detergent compound is an alkaline earth metal salicylate or sulphonate compound, leading to improvement of the energy efficiency of the resulting fluid, as hereinbefore described.
• the essential detergents that are generally employed in the invention are exemplified by oil-soluble neutral or overbased salts of alkaline earth metals with one or more hydrocarbyl-substituted sulfonic acids or salicylic acids.
• the preferred salts of such acids from the cost-effectiveness, toxicological, and environmental standpoints are the salts of calcium and magnesium.
• the preferred salts useful with this invention are either neutral or overbased salicylate salts of calcium or magnesium.
• Oil-soluble neutral metal-containing detergents are those detergents that contain stoichiometrically equivalent amounts of metal in relation to the amount of acidic moieties present in the detergent. Thus, in general the neutral detergents will have a low basicity when compared to their overbased counterparts.
• overbased in connection with metallic detergents is used to designate metal salts wherein the metal is present in stoichiometrically larger amounts than the organic radical.
• the commonly employed methods for preparing the over-based salts involve heating a mineral oil solution of an acid with a stoichiometric excess of a metal neutralizing agent such as the metal oxide, hydroxide, carbonate, bicarbonate, of sulfide at a temperature of about 50°C, and filtering the resultant product.
• a "promoter” in the neutralization step to aid the incorporation of a large excess of metal likewise is known.
• Examples of compounds useful as the promoter include phenolic substances such as phenol, naphthol, alkyl phenol, thiophenol, sulfurized alkylphenol, and condensation products of formaldehyde with a phenolic substance; alcohols such as methanol, 2-propanol, octanol, Cellosolve alcohol, Carbitol alcohol, ethylene glycol, stearyl alcohol, and cyclohexyl alcohol; and amines such as aniline, phenylene diamine, phenothiazine, phenyl-beta-naphthylamine, and dodecylamine.
• a particularly effective method for preparing the basic salts comprises mixing an acid with an excess of a basic alkaline earth metal neutralizing agent and at least one alcohol promoter, and carbonating the mixture at an elevated temperature such as 60 to 200°C.
• suitable metal-containing detergents are neutral and overbased salts of calcium sulfonates and magnesium sulfonates wherein each sulfonic acid moiety is attached to an aromatic nucleus which in turn usually contains one or more aliphatic substituents to impart hydrocarbon solubility, and calcium salicylates and magnesium salicylates wherein the aromatic moiety is usually substituted by one or more aliphatic substituents to impart hydrocarbon solubility.
• Mixtures of neutral or over-based salts of two or more different alkaline earth metals can be used.
• neutral and/or overbased salts of mixtures of two or more different acids e.g. one or more overbased calcium salicylates with one or more overbased calcium sulfonates
• overbased metal detergents are generally regarded as containing overbasing quantities of inorganic bases, probably in the form of micro dispersions or colloidal suspensions.
• oil soluble as applied to metallic detergents is intended to include metal detergents wherein inorganic bases are present that are not necessarily completely or truly oil-soluble in the strict sense of the term, inasmuch as such detergents when mixed into base oils behave much the same way as if they were fully and totally dissolved in the oil.
• the metallic detergents utilized in this invention can, if desired, be oil-soluble boronated neutral and/or overbased alkali of alkaline earth metal-containing detergents.
• Methods for preparing boronated metallic detergents are described in, for example, U.S. Pat. Nos. 3,480,548 ; 3,679,584 ; 3,829,381 ; 3,909,691 ; 4,965,003 ; 4,965,004 .
• Preferred metallic detergents for use with this invention are calcium sulfonates and/or magnesium sulfonates, and calcium and/or magnesium salicylates.
• at least one such alkaline earth metal detergent compound is a calcium salicylate or calcium sulphonate compound.
• the total amount of the alkaline earth metal detergent compound(s) present in the transmission fluid composition is such as to provide the transmission fluid composition with a an alkaline earth metal content of between 50 and 250 parts per million by weight, per weight of the transmission fluid composition.
• each alkaline earth metal detergent compound present in the transmission fluid composition is a neutral or overbased calcium salicylate compound.
• Salicylate compounds have been found to be particularly advantageous in combination with the additives (ii) and (iii) described herein and contribute to the fuel efficiency advantage of the present invention.
• each alkaline earth metal detergent compound present in the transmission fluid composition is a neutral or overbased calcium salicylate compound, and wherein the total amount of the calcium salicylate compound(s) present is such as to provide the transmission fluid composition with a calcium content of between 50 and 250 parts per million by weight, per weight of the transmission fluid composition, this amount having been found to provide optimal efficiency gains.
• Dispersants specifically those characterised as ashless dispersants, are also useful in this invention as components of additive (iv).
• Suitable dispersants include long chain (i.e. greater than forty carbon atoms) substituted hydrocarbyl succinimides and hydrocarbyl succinamides, mixed ester/amides of long chain (i.e. greater than forty carbon atoms) hydrocarbyl-substituted succinic acid, hydroxyesters of such hydrocarbyl-substituted succinic acid, and Mannich condensation products of long chain (i.e. greater than forty carbon atoms) hydrocarbyl-substituted phenols, formaldehyde and polyamines. Mixtures of such dispersants can also be used.
• the preferred dispersants are the long chain alkenyl succinimides. These include acyclic hydrocarbyl substituted succinimides formed with various amines or amine derivatives such as are widely disclosed in the patent literature. Use of alkenyl succinimides which have been treated with an inorganic acid of phosphorus (or an anhydride thereof) and a boronating agent are also suitable for use in the compositions of this invention as they are much more compatible with elastomeric seals made from such substances as fluoroelastomers and silicon-containing elastomers.
• Polyisobutenyl succinimides formed from polyisobutenyl succinic anhydride and an alkylene polyamine such as triethylene tetramine or tetraethylene pentamine wherein the polyisobutenyl substituent is derived from polyisobutene having a number average molecular weight in the range of 500 to 5000 (preferably 800 to 2500) are particularly suitable.
• Dispersants may be post-treated with many reagents known to those skilled in the art. (see, e.g., U.S. Pat. Nos. 3,254,025 , 3,502,677 and 4,857,214 ).
• Anti-wear additives useful in this invention as components in additive (iv) are typically oil-soluble phosphorus-containing compounds that, in the context of this invention, may vary widely and are not limited by chemical type. The only limitation is that the material be oil soluble so as to permit the dispersion and transport of phosphorus-containing compound within the lubricating oil system to its site of action.
• Suitable phosphorus compounds are: phosphites and thiophosphites (mono-alkyl, di-alkyl, tri-alkyl and partially hydrolyzed analogs thereof); phosphates and thiophosphates; amines treated with inorganic phosphorus such as phosphorous acid, phosphoric acid or their thio analogs; zinc dithiodiphosphates; amine phosphates.
• phosphorus compounds include: mono-n-butyl-hydrogen-acid-phosphite; di-n-butyl-hydrogen phosphite; triphenyl phosphite; triphenyl thiophosphite; tri-n-butylphosphate; dimethyl octadecenyl phosphonate, 900MW polyisobutenyl succinic anhydride (PIBSA) polyamine dispersant post treated with H 3 PO 3 and H 3 BO 3 (see e.g., U.S. 4,857,214 ); zinc (di-2-ethylhexyldithiophosphate).
• PIBSA polyisobutenyl succinic anhydride
• the preferred oil soluble phosphorus compounds are the esters of phosphoric and phosphorous acid. These materials would include the di-alkyl, tri-alkyl and tri-aryl phosphites and phosphates.
• a preferred oil soluble phosphorus compound is the mixed thioalkyl phosphite esters, for example as produced in U.S. 5,314,633 , incorporated herein by reference.
• the phosphorus compounds of the invention can be used in the oil in any effective amount. However, a typical effective concentration of such compounds would be that delivering from about 5 to about 5000 ppm phosphorus into the oil. A preferred concentration range is from about 10 to about 1000 ppm of phosphorus in the finished oil and the most preferred concentration range is from about 50 to about 500 ppm.
• Preferred friction modifiers useful as components in additive (iv) comprise a reaction product of an isomerized alkenyl substituted succinic anhydride and a polyamine characterized by structure (I), where structure (I) is: where x and y are independent integers whose sum is from 1 to 30, and z is an integer from 1 to 10.
• the starting components for forming the structure (I) compounds are isomerized alkenyl succinic anhydrides which are prepared from maleic anhydride and internal olefins i.e., olefins which are not terminally unsaturated and therefore do not contain the moiety. These internal olefins can be introduced into the reaction mixture as such, or they can be produced in situ by exposing alpha-olefins to isomerization catalysts at high temperatures. A process for producing such materials is described in U.S. 3,382,172 .
• the isomerized alkenyl substituted succinic anhydrides have the structure shown as structure (II), where structure (II) is represented by: where x and y are independent integers whose sum is from 1 to 30.
• the preferred succinic anhydrides are produced from isomerization of linear alpha-olefins with an acidic catalyst followed by reaction with maleic anhydride.
• the preferred alpha-olefins are 1-octene, 1-decene, 1-dodecene, 1- tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane, or mixtures of these materials.
• the products described can also be produced from internal olefins of the same carbon numbers, 8 to 20.
• the isomerized alkenyl succinic anhydrides are then further reacted with polyamines of structure (III), where structure (III) is represented by: where z is an integer from 1 to 10, preferably from 1 to 3.
• the preferred products of this invention employ diethylene triamine, triethylene tetramine, tetraethylene pentamine or mixtures thereof.
• the isomerized alkenyl succinic anhydrides (II) are typically reacted with the amines in a 2:1 molar ratio so that both primary amines are converted to succinimides. Sometimes a slight excess of isomerized alkenyl succinic anhydride (II) is used to insure that all primary amines have reacted. The products of the reaction are shown as structure (I).
• the di-succinimides of structure (I) may be further post-treated by any number of techniques known in the art. These techniques would include, but not be limited to: boration, maleation, acid treating with inorganic acids such as phosphoric, phosphorous, and sulfuric. Descriptions of these processes can be found in, for example, U.S. 3,254,025 ; U.S. 3,502,677 ; U.S. 4,686,054 ; and U.S. 4,857,214 .
• any effective amount of the compounds of structure (I) and its derivatives may be used in additive (iv) of this invention, typically these effective amounts will range from 0.5 to 10, preferably from 2 to 7, most preferably from 3 to 6 weight percent of the finished fluid.
• additive (iv) of this invention may be combined in the form of a concentrate.
• the active ingredient (a.i.) level of the concentrate will range from 20 to 90%, preferably from 25 to 80%, most preferably from 35 to 75 weight percent of the concentrate.
• the balance of the concentrate is a diluent typically comprised of a diluent or solvent.
• the process of the present invention provides for the manufacture of a transmission fluid composition, the composition consisting of :
• the resulting composition is an automotive transmission fluid, and more preferably the additions in step b) improve the efficiency of power transmission provided by the composition when in use as an automotive transmission fluid, as demonstrated by an increase in the fuel efficiency of the vehicle during operation.
• the polyalphaolefin compound(s) (iii) are preferably mixed with one or more of the detergent additives (iv) to form a single additive concentrate prior to addition to the lubricating oil or blend of oils.
• the total amount of the polyalphaolefin compound or compounds (iii) mixed with the lubricating oil or blend of lubricating oils is in the range of 2 to 3 percent by weight of the transmission fluid composition.
• each alkaline earth metal detergent compound mixed with the transmission fluid composition is a neutral or overbased calcium salicylate compound. More preferably, when each alkaline earth metal detergent compound mixed with the transmission fluid composition is a neutral or overbased calcium salicylate compound, the total amount of calcium salicylate compound(s) mixed with the lubricating oil or blend of lubricating is such as to provide the transmission fluid composition with a calcium content of between 50 and 250 parts per million by weight, per weight of the transmission fluid composition.
• the invention further provides a method of improving the energy efficiency of a transmission, comprising the use therein of the transmission fluid composition defined in the first aspect, or of the transmission fluid composition obtained by the process of the second aspect.
• the transmission is a transmission for an automotive vehicle
• the improvement in energy efficiency is an increase in fuel economy of the vehicle during operation.
• the invention further provides an additive concentrate for a transmission fluid, the concentrate consisting of a suitable carrier liquid, (ii) a viscosity modifier or blend of viscosity modifiers, and (iii) a polyalphaolefin compound or mixture of polyalphaolefin compounds made by the metallocene-catalysed polymerisation of an alphaolefin feedstock, and (iv) one or more detergent additives, at least one of which comprises one or more alkaline earth metal detergent compounds wherein at least one alkaline earth metal detergent compound is an alkaline earth metal salicylate or sulphonate compound; wherein the total amount of polyalphaolefin compound(s) (iii) present in the concentrate is such that, after addition of the concentrate at its specified treat rate to the transmission fluid, said compounds (iii) constitute no more than 4 percent by weight of the resulting transmission fluid composition.
• the total amount of the polyalphaolefin compound or compounds (iii) in the additive concentrate is such that,
• each alkaline earth metal detergent compound present in the concentrate is a neutral or overbased calcium salicylate compound.
• Table 1 Component (% by weight, per weight of finished composition) Composition 1 Composition 1C (comparative) Composition 2 Composition 2C (comparative) Base lubricating oil 83.7 86.3 83.3 85.1 Viscosity modifier 3.0 3.0 2.0 4.2 Pour point depressant 0.3 0.2 0.2 0.2 mPolyalphaolefin 2.5 - 4.0 - Detergent additive : - Overbased calcium salicylate 0.08 0.08 0.08 0.08 - Overbased calcium sulphonate - - - - - Other components 10.42 10.42 10.42 10.42 10.42 KV 40°C 19.84 17.73 19.23 18.69 KV 100°C 4.77 4.37 4.63 4.69
• the base lubricating oil, viscosity modifier, pour point depressant and detergent additive were the same in each case, and the blends differed only in the relative proportions of these constituents and, in the case of Compositions 1C and 2C, in the absence of the mPAO.
• the mPolyalphaolefin was Spectrosyn EliteTM 150, an item of commerce from Exxonmobil Chemical Company.
• the detergent additive contained overbased calcium salicylate and additionally contained other components being dispersant, anti-wear, and other minor active components typical of a detergent additive package, combined with a small amount of base oil and diluent. These other components of the detergent additive were the same in each case.
• the viscosity modifier was VISCOPLEX ® 12-199, available as an item of commerce from Evonik Rohmax USA, Inc and falling within the class (ii)(c) described earlier in relation to suitable viscosity modifiers.
• the pour point depressant was a typical commercially available material and the same in each case.
• a bench-test experiment called the "FE-8" test measures the torque required to rotate a radial thrust roller bearing assembly lubricated by the transmission fluid in question.
• the efficiency of the formulations was tested by measuring torque to rotate the cylindrical roller bearings at various conditions using an FE-8 radial thrust roller bearing tester.
• the bearings used are 15 roller FAG/INA 81212 bearings.
• the bearings were installed in the test rig and then pre-loaded to 60 kN. The bearings are run-in for 20 hours at 500 rpm at 100°C priot to taking any measurement.
• test head For each test fluid, the test head is heated until the bearing temperature reaches 40°C. While maintaining this temperature, bearings are rotated at 10 rpm for 10mins then at 100rpm and 500rpm for 5 mins each. The reported torque at each condition is calculated by averaging the torque reading during the last 1 minute of the condition. Temperature is then increased to 80°C and then finally to 120°C and torque is measured with the same procedure at the three speeds. After this, the rig is cooled down to room temperature and the whole process is repeated. Final test results are the average of two repeats at each temperature and speed.
• the FE-8 test thus compares the energy requirements needed to achieve defined bearing rotation with different fluids. Achieving the defined rotations with lower applied torque indicates greater energy efficiency within the mechanical system.
• a vehicle test experiment was conducted according to the standard US Federal Test Procedure 75 ("FTP 75").
• FTP 75 US Federal Test Procedure 75
• a commercially-available SUV with six speed automatic transmission was repeatedly run on a vehicle dynamometer according to the operating cycle specified in FTP 75, and in each case the improvement in fuel economy observed for the transmission fluid employed in the test is reported (as % improvement) over a reference fluid.
• the FTP 75 provides a direct measure of fuel economy observed in vehicle operation. A positive percentage indicates greater fuel efficiency compared to reference.
• composition 1 consistently required lower applied torque to achieve rotations of 100 and 500 rpm in the FE-8 test, indicating improved energy efficiency for composition 1 (with polyalphaolefin (iii) at 2.5%) as compared to compositions 1C (and 2C) (no polyalphaolefin (iii)).
• polyalphaolefin (iii) shows an overall benefit for energy efficiency.
• compositions 1C and 2C further demonstrates that the small residual differences in the KV values of these samples do not account for the differences in torque seen between composition 1 and composition 1C, which must therefore be attributable to the effect of polyalphaolefin (iii).
• composition 2C had a KV 100 of 4.69, almost identical to that of composition 1 (4.77), yet at 120°C the torque results for composition 2C are even higher than those for composition 1C, indicating that the better results obtained for composition 1 cannot be explained by reference to viscosity behaviour per se.
• composition 1 polyalphaolefin (iii) at 2.5%) was compared to the test reference fluid (contains no polyalphaolefin (iii)) and to composition 2 ((polyalphaolefin (iii) at the higher treat rate of 4%).
• the percentage improvement in fuel economy over the whole test was 0.86% for composition 1, compared to only 0.42% for composition 2.
• the fuel efficiency benefit of polyalphaolefin (iii) in the composition showed an optimum at the treat rate of 2.5%, and at a higher treat rate of 4% the fuel efficiency benefit had dropped off considerably, confirming the benefit seen is one attributable to additive-level proportions of polyalphaolefin (iii).
• Table 3 Component (% by weight, per weight of finished composition) Composition 3 Composition 4 Composition 5 Base lubricating oil 83.8 83.8 83.8 Viscosity modifier 3.0 3.0 3.0 Pour point depressant 0.2 0.2 0.2 mPolyalphaolefin 2.5 2.5 2.5 Detergent additive : - Overbased calcium salicylate 0.11 0.16 - - Overbased calcium sulphonate - - 0.09 - Other components 10.39 10.34 10.41 KV 40°C 19.92 19.99 19.67 KV 100°C 4.76 4.77 4.72 Note: in these formulations, the amount of diluent in the detergent additive was adjusted to compensate for the variation in salicylate or sulphonate level, this change being reflected in the slight variation in the amount of 'other components
• Composition 1 (from Example 1 above, calcium salicylate present to the treat rate of 100ppm calcium) showed a fuel economy improvement over the total FTP 75 test of 0.86%.
• Composition 3 (higher calcium salicylate treat rate, 140ppm calcium) showed a significantly greater improvement of 1.47%, whilst a further increase in calcium salicylate to a treat rate of 200ppm calcium (Composition 4) caused the fuel economy result to drop back to 0.49%.
• Composition 4 shows a further increase in calcium salicylate to a treat rate of 200ppm calcium (Composition 4) caused the fuel economy result to drop back to 0.49%.
• US-A-2010/0035778 (to GM global technology operations Inc.) exemplifies a composition comprising 9.4% (by weight, per total weight of fluid) of a first polyalphaolefin (PAO 2cSt) and 68.0% of a second polyalphaolefin (PAO 6cSt), together with proprietary additives comprising the additive package Hitec® 3491 plus viscosity index improver and ester to a total of 22.6% by weight of the composition.
• PAO 2cSt first polyalphaolefin
• PAO 6cSt second polyalphaolefin
• Composition 1 of the present invention was compared to a commercially-obtained GM automatic transmission fluid (GM ATF 212-B), having a reported PAO composition the same as that of the example from US-A-2010/0035778 , and likewise a total additive content of 22.6% (Hitec 3941A). The applicant therefore regards this as illustrative of the invention exemplified in US-A-2010/0035778 .
• Composition 1 showed substantially better fuel economy than the invention described in US-A-2010/0035778 .
• US-A-2010/0035778 teaches a solution for fuel economy that requires the blend of two PAOs of differing viscosities as the basestock for the transmission fluid. As shown by the above results, a greater improvement in fuel economy is surprisingly obtained from the composition of the present invention, through the use of only a small (additive) quantity of the specific mPAO (iii) in combination with the other essential components.

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