Background

[0001] Hydraulic fluid compositions contain a number of surface-active additives to provide protection for mechanical systems from wear and corrosion. For example, the hydraulic fluid composition includes additives to protect the mechanical system from rust. In addition, for hydraulic fluid compositions subject to water contamination and turbulence, the ability of the water and oil to separate is important. Therefore, it is desirable to provide hydraulic fluid compositions which provide protection from rust as well as excellent demulsibility performance.

Summary of the Invention

[0002] The present invention provides a fluid composition for use in a hydraulic system, turbine system, or a circulating oil system. A hydraulic system is generally a device or apparatus in which pressure is applied to a fluid, typically an oil-based fluid, to transmit energy to different parts of the system. A turbine lubricant is typically used to lubricate the gears or other moving parts of a turbine (or turbine system), such as a steam turbine or a gas turbine. A circulating oil is typically used to distribute heat to or through a device or apparatus through which it is circulated.

[0003] The hydraulic fluid composition of the present invention comprises an oil of lubricating viscosity, a polyalkenyl surfactant, and a hydrocarbyl amine salt of alkyl phosphoric acid. In one embodiment, the polyalkenyl surfactant employed in the present invention comprises a functional group selected from the group consisting of imides, amides, esters, anhydrides, or mixtures thereof, for example, the polyalkenyl surfactant may comprise a polyamine polyisobutenyl succinimide, a polyisobutenyl succinic anhydride surfactant, or a combination of a polyamine polyisobutenyl succinimide and a polyisobutenyl anhydride. In one embodiment, the hydrocarbyl amine salt of alkyl phosphoric acid comprises a hydrocarbyl amine salt of alkylphosphoric acid, a hydrocarbyl amine salt of dialkylphosphoric acid, or mixtures thereof. The hydrocarbyl amine salt of alkyl phosphoric acid may be present in an amount sufficient to deliver 25 to 800ppm, or 50 to 500ppm, or 100 to 400ppm phosphorous to the hydraulic fluid composition. Further, the hydraulic fluid composition of the present invention may have ISO viscosity grade of 68 to 460 or 100 to 220. [0004] The lubricating composition may also include additional additives as further explained herein.

[0005] The present invention also provides a method of lubricating a hydraulic system or a method of operating a hydraulic system wherein the methods comprise comprising supplying to the hydraulic system a hydraulic fluid composition as described herein.

[0006] Specific features and other aspects of the invention are described in more detail in the following Detailed Description of the Invention.

Detailed Description of the Invention

Oils of Lubricating Viscosity

[0007] The lubricant compositions disclosed herein comprise an oil of lubricating viscosity. Suitable oils include natural and synthetic lubricating oils and mixtures thereof. In a fully formulated lubricant, the oil of lubricating viscosity is generally present in a major amount (i.e., an amount greater than 50 percent by weight). Typically, the oil of lubricating viscosity is present in an amount of 70 to 99.5 percent by weight, and often greater than 80 percent by weight of the overall composition. The oil of lubricating viscosity is generally used as a “base oil” of the lubricant composition and makes up 100 parts by weight (pbw) of the overall composition with the pbw ranges for the other components being provided with this 100 pbw of base oil in mind. In other embodiments the pbw ranges of the various components, including the base oils, are provided such that the total of the pbw of all components is 100, and thus the pbw values are equivalent to percent by weight values. The pbw ranges provided for the various components described below may be taken either way, however in most embodiments they are to be read so as to be equivalent to percent by weight values.

[0008] The oil of lubricating viscosity may include natural and synthetic oils, oil derived from hydrocracking, hydrogenation, and hydrofinishing, unrefined, refined and re-refined oils or mixtures thereof. Unrefined oils are those obtained directly from a natural or synthetic source generally without (or with little) further purification treatment. Refined oils are similar to the unrefined oils except they have been further treated in one or more purification steps to improve one or more properties. Purification techniques are known in the art and include solvent extraction, secondary distillation, acid or base extraction, filtration, percolation and the like. Re-refined oils are also known as reclaimed or reprocessed oils and are obtained by processes similar to those used to obtain refined oils and often are additionally processed by techniques directed to removal of spent additives and oil breakdown products.

[0009] Natural oils useful as the oil of lubricating viscosity include animal oils, vegetable oils (e.g., castor oil, lard oil), mineral lubricating oils such as liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic naphthenic types and oils derived from coal or shale or mixtures thereof.

[0010] Synthetic oils of lubricating viscosity include hydrocarbon oils such as polymerized and interpolymerised olefins (e.g., polybutylenes, polypropylenes, propyleneisobutylene copolymers); poly(l -hexenes), poly(l-octenes), poly(l- decenes), and mixtures thereof; alkyl-benzenes (e.g., dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl)-benzenes); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyls); alkylated biphenyl ethers and alkylated biphenyl sulfides and the derivatives, analogs and homologs thereof or mixtures thereof.

[0011] Another synthetic oil of lubricating viscosity includes polyol esters other than the hydrocarbyl-capped polyoxyalkylene polyol as disclosed herein, dicarboxylic esters, liquid esters of phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, and the diethyl ester of decane phosphonic acid), or polymeric tetrahydrofurans. Synthetic conventional oils of lubricating viscosity also include those produced by Fischer-Tropsch reactions and typically may be hydroisomerised Fischer-Tropsch hydrocarbons or waxes. In one embodiment, the oil of lubricating viscosity may be prepared by a Fischer-Tropsch gas-to-liquid synthetic procedure as well as other gas-to-liquid oils.

[0012] Oils of lubricating viscosity may further be defined as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. The five base oil groups are as follows: Group I (sulfur content >0.03 wt %, and/or <90 wt % saturates, viscosity index 80-120); Group II (sulfur content <0.03 wt % and >90 wt % saturates, viscosity index 80-120); Group III (sulfur content <0.03 wt % and >90 wt % saturates, viscosity index >120); Group IV (all polyalphaolefins PAOs such as PAO- 2, PAO-4, PAO-5, PAO-6, PAO-7 or PAO-8); and Group V. In some embodiments, the oil of lubricating viscosity includes API Group I, Group II, Group III, Group IV, Group V oil or mixtures thereof. In other embodiments, the oil of lubricating viscosity is an API Group I, Group II, Group III, Group IV oil or mixtures thereof. In still other embodiments, the oil of lubricating viscosity is often an API Group II, Group III or Group IV oil or mixtures thereof. In one embodiment, the oil of lubricating viscosity comprises or consist of a Group I base oil. In another embodiment, the oil of lubricating viscosity comprises or consists of a Group II base oil. In another embodiment, the oil of lubricating viscosity comprises or consist of a Group III base oil. Further, in one embodiment, the oil of lubricating viscosity comprises or consists of a Group IV base oil.

[0013] The various described oils of lubricating viscosity may be used alone or in combinations. The oil of lubricating viscosity is used in the range of about 70 wt% to about 99.5 wt%, and in another embodiment, in the range of about 75 wt% to about 98 wt%, in another embodiment in the range of about 88 wt% to about 97 wt% of the lubricant composition.

[0014] In concentrate compositions, typically the amount of additives and other components remains the same, but the amount of oil of lubricating viscosity is reduced, in order to make the composition more concentrated and more efficient to store and/or transport. A person skilled in the art would be able to easily adjust the amount of oil of lubricating viscosity present in order to provide a concentrate and/or additive composition. Surfactant

[0015] The hydraulic fluid composition of the present invention also includes a polyalkenyl surfactant. Surfactants which may be included in the composition include those with an oil soluble polymeric hydrocarbon backbone and having functional groups that are capable of associating with particles to be dispersed in the oil. Exemplary functional groups include amines, alcohols, amides, imides, anhydrides, and ester polar moieties which are attached to the polymer backbone, often via a bridging group. Suitable surfactants include polyetheramines, borated succinimides, non-borated succinimides, Mannich reaction products of a dialkylamine, an aldehyde and a hydrocarbyl substituted phenol, or combinations thereof. The surfactant is included in the hydraulic fluid composition of the present invention in amounts of from 100 ppm to 2500 ppm.

[0016] In one embodiment, the surfactant comprises a dispersant. Example dispersants include polyalkylene succinimides as described in U.S. Patent Nos. 5,851,965, 5,853,434, and 5,792,729; amines as described in U.S. Patent Nos. 3,219,666, 3,565,804, and 5,633,326; anhydrides as described in U.S. Patent Nos. 4,234,435, 3,172,892, 3,215,707, 3,361,673, and 3,401,118; ashless succinimide dispersants described in U.S. Patent Nos. 4,234,435 and 4,636,322; Mannich dispersants, described in U.S. Patent Nos. 3,697,574 and 3,736,357; Koch dispersants, described in U.S. Patent Nos. 5,936,041, 5,643,859, and 5,627,259.

[0017] In one embodiment, the surfactant comprises or consists of a polyamine polyisobutenyl succinimide. In another embodiment, the surfactant comprises or consists of a polyisobutenyl succinic anhydride surfactant. In another embodiment, the surfactant comprises or consists of a mixture of a polyamine polyisobutenyl succinimide and a polyisobutenyl succinic anhydride.

Hydrocarbyl Amine Salt of Alkyl Phosphoric Acid

[0018] The hydraulic fluid composition of the present invention also includes a hydrocarbyl amine salt of alkyl phosphoric acid. Examples of suitable compounds include hydrocarbyl amine salts of alkylphosphoric acid, hydrocarbyl amine salts of dialkylphosphoric acid, hydrocarbyl amine salts of dialkyldithiophosphoric acid, or mixtures thereof.

[0019] Suitable hydrocarbyl amine salts of alkylphosphoric acid may be represented by the following formula: wherein R ²⁶ and R ²⁷ are independently hydrogen, alkyl chains or hydrocarbyl, typically at least one of R ²⁶ and R ²⁷ are hydrocarbyl. R ²⁶ and R ²⁷ contain 4 to 30, or 8 to 25, or 10 to 20, or 13 to 19 carbon atoms. R ²⁸ , R ²⁹ and R ³⁰ are independently hydrogen, alkyl branched or linear alkyl chains with 1 to 30, or 4 to 24, or 6 to 20, or 10 to 16, or 12 to 14 carbon atoms. R ²⁸ , R ²⁹ and R ³⁰ are independently hydrogen, alkyl branched or linear alkyl chains, or at least one, or two of R ²⁸ , R ²⁹ and R ³⁰ are hydrogen.

[0020] Examples of alkyl groups suitable for R ²⁸ , R ²⁹ and R ³⁰ include butyl, sec butyl, isobutyl, tert-butyl, pentyl, n-hexyl, sec hexyl, n-octyl, 2-ethyl, hexyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, octadecenyl, nonadecyl, eicosyl or mixtures thereof.

[0021] In one embodiment the hydrocarbyl amine salt of an alkylphosphoric acid is the reaction product of a C14 to Cis alkylated phosphoric acid with Primene® 81R (produced and sold by Rohm & Haas) which is a mixture of Cn to C14 tertiary alkyl primary amines.

[0022] Hydrocarbyl amine salts of dialkyldithiophosphoric acid may include the reaction product of heptyl or octyl or nonyl dithiophosphoric acids with ethylene diamine, morpholine or Primene® 81R or mixtures thereof.

[0023] The hydrocarbyl amine salt of alkyl phosphoric acid is present in the hydraulic fluid composition in amounts sufficient to deliver 25 ppm to 800 ppm phosphorous to the hydraulic fluid composition. In some embodiments, the hydrocarbyl amine salt of alkyl phosphoric acid is present in the hydraulic fluid composition in amounts sufficient to deliver 50 ppm to 500 ppm or even 100 ppm to 400 ppm or even 300 to 400 phosphorous to the hydraulic fluid composition.

Other Additives

[0024] The hydraulic fluid composition of the invention may be in the form of a concentrate and/or a fully formulated lubricant. If the lubricant composition of the invention (comprising the additives disclosed herein) is in the form of a concentrate (which may be combined with additional oil to form, in whole or in part, a finished lubricant), the ratio of the of these additives to the oil of lubricating viscosity and/or to diluent oil include the ranges of 1 :99 to 99: 1 by weight, or 80:20 to 10:90 by weight.

[0025] In addition to the additives described above, the hydraulic fluid composition may also contain one or more additional other additives. In some embodiments the additional additives may include ashless anti-wear additives different from the hydrocarbyl amine salt of alkyl phosphoric acid described above, antioxidant, corrosion inhibitor, rust inhibitor, foam inhibitor, demulsifier, metal deactivator, friction modifier, metal -containing detergent, emulsifier, pour point depressant, viscosity modifier, or any combination thereof.

[0026] In one embodiment, the hydraulic fluid of the present invention comprises a metal -free phosphorous containing anti -wear agent that is different from the hydrocarbyl amine salt of alkyl phosphoric acid described above. Examples of such suitable anti-wear agents include tartrates, tartrimides, oil soluble amine salts of phosphorus compounds, sulfurized olefins, phosphites (such as dibutyl or dioleyl phosphite), phosphonates, thiocarbamate-containing compounds, such as thiocarbamate esters, thiocarbamate amides, thiocarbamic ethers, alkylene-coupled thiocarbamates, bis(S-alkyldithiocarbamyl) disulfides, and oil soluble phosphorus amine salts. In one embodiment, the metal-free phosphorous anti-wear agent comprises or consists of a (thio)phosphate ester. As used herein, the term (thio)phosphate ester should be understood to include phosphate esters, thiophosphate esters or mixtures thereof.

[0027] Phosphorus compounds usable in the present invention may include triaryl phosphate or triaryl thiophosphate represented by a formula (1) below:

[0028] In the formula (1), R is a hydrogen atom or an alkyl group having 3 to 9 carbon atoms, for example 3, 4, 5, 6, 7, 8, 9, or combinations thereof of carbon atoms and X is an oxygen atom or a sulfur atom. In the formula (1), the three R groups may be mutually the same or different. Examples of the alkyl group having 4 or less carbon atoms include a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group and tertiary butyl group.

[0029] Examples of the phosphorus compound represented by the formula (1) include triphenyl phosphate, tricresyl phosphate, triphenyl thiophosphate, tricresyl thiophosphate, and butylated triphenyl phosphorothionate.

[0030] Another example of a phosphorous compound useful in the present invention is represented by a formula (2) below. [0031] In the formula (2), R ¹ represents a linear or branched alkylene group having 1 to 8 carbon atoms, R ² and R ³ each represent a hydrocarbon group having 3 to 20 carbon atoms, and X ² and X ³ each, independently, represent an oxygen atom or sulfur atom.

[0032] In one embodiment, R ¹ may be a linear or branched alkylene group having 1 to 8 carbon atoms, more preferably a linear or branched alkylene group having 2 to 4 carbon atoms, and further preferably a branched alkylene group. Specifically, R ¹ is preferably, for instance, — CH ₂ CH ₂ — , — CH ₂ CH(CH ₃ )— , — CH ₂ CH(CH ₂ CH ₃ )— or — CH ₂ CH(CH ₂ CH ₂ CH ₃ ) — , and more preferably — CH ₂ CH(CH ₃ ) — or — CH ₂ CH(CH ₃ )CH ₂ — .

[0033] In one embodiment, R ² to R ³ each preferably represent a linear or branched alkyl group having 3 to 8 carbon atoms, and more preferably a linear or branched alkyl group having 4 to 6 carbon atoms. Specifically, R ² to R ³ is each preferably selected from the group consisting of propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl, hexyl, 2-ethylbutyl, 1- methylpentyl, 1,3 -dimethylbutyl and 2-ethylhexyl groups.

[0034] In one embodiment, both X ² and X ³ represent oxygen atoms. In another embodiment, both X ² and X ³ represent sulfur atoms. In another embodiment, X ² is oxygen and X ³ is sulfur, and in another embodiment, X ² is sulfur and X ³ is oxygen.

[0035] Another phosphorous compound which may be useful in the present invention comprises a thiophosphate compound represented by a formula (3) below.

[0036] In the formula (3), R ⁴ , R ⁵ and R ⁷ are each independently a linear or branched saturated or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms or a branched or unbranched saturated or unsaturated cyclic hydrocarbon group having 5 to 18 carbon atoms. R ⁶ is a linear or branched alkylene group having 1 to 8 carbon atoms, X ⁴ and X ⁵ are each independently an oxygen atom or sulfur atom. In one embodiment of formula

(3), at least one sulfur atom exists. [0037] In one embodiment, both X ⁴ and X ⁵ represent oxygen atoms. In another embodiment, both X ⁴ and X ⁵ represent sulfur atoms. In another embodiment, X ⁴ is oxygen and X ⁵ is sulfur, and in another embodiment, X ⁴ is sulfur and X ⁵ is oxygen.

[0038] In one embodiment, the metal-free anti-wear agent of the present invention may be selected from Methyl 3-((dialkoxyphosphorothioyl)thio)propanoate with mixed C4/C5 alkoxy groups, 3-((diisobutoxyphosphorothioyl)thio)-2- methylpropanoic acid, and mixtures thereof.

[0039] In another embodiment, the hydraulic fluid of the invention may also include a metal-containing anti-wear agent, which may include a metal dialkyldithiophosphate. Typically, the metal dialkyldithiophosphate may be a zinc dialkyldithiophosphate (ZDDP), or mixtures thereof. Zinc dialkyldithiophosphates are known in the art.

[0040] The hydraulic fluid of the present invention will contain up to 800ppm phosphorous. When included in the hydraulic fluids of the present invention, the anti-wear additives described may be present in amounts sufficient to provide 10 ppm to 500 ppm phosphorous or even 50 ppm to 500 ppm or even 300 to 400 ppm by weight phosphorous. If the anti-wear agents are the only phosphorous containing compound present in the hydraulic fluid, such compounds will be present in amounts sufficient to deliver the required amount of phosphorous. In one embodiment, the anti-wear agents are metal-free, in particular, zinc free. In some embodiments, the hydraulic fluid composition is substantially free of zinc, or contains less than 10 ppm or even less than 5 ppm zinc.

[0041] The hydraulic fluid composition may also contain an antioxidant. If present, the antioxidant may be present at 0 wt % to 4.0 wt %, or 0.02 wt % to 3.0 wt %, or 0.03 wt % to 1.5 wt % of the hydraulic fluid composition.

[0042] Antioxidants include diarylamine, alkylated diarylamines, hindered phenols, molybdenum compounds (such as molybdenum dithiocarbamates), hydroxyl thioethers, trimethyl polyquinoline (e.g., l,2-dihydro-2,2,4-trimethylquinoline), or mixtures thereof.

[0043] The diarylamine or alkylated diarylamine may be a phenyl-a-naphthylamine (PANA), an alkylated diphenylamine, or an alkylated phenylnaphthylamine, or mixtures thereof. The alkylated diphenylamine may include di-nonylated diphenylamine, nonyl diphenylamine, octyl diphenylamine, di-octylated diphenylamine, di-decylated diphenylamine, decyl diphenylamine, benzyl diphenylamine and mixtures thereof. In one embodiment the diphenylamine may include nonyl diphenylamine, dinonyl diphenylamine, octyl diphenylamine, dioctyl diphenylamine, or mixtures thereof. In one embodiment the alkylated diphenylamine may include nonyl diphenylamine, or dinonyl diphenylamine. The alkylated diarylamine may include octyl, di-octyl, nonyl, di-nonyl, decyl or di-decyl phenylnaphthylamines. In one embodiment, the diphenylamine is alkylated with a benzene and t-butyl substituent.

[0044] The hindered phenol antioxidant often contains a secondary butyl and/or a tertiary butyl group as a sterically hindering group. The phenol group may be further substituted with a hydrocarbyl group (typically linear or branched alkyl) and/or a bridging group linking to a second aromatic group. Examples of suitable hindered phenol antioxidants include 2,6-di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6- di-tert-butylphenol, 4-propyl-2,6-di-tert-butylphenol or 4-butyl-2,6-di-tert-butylphenol, or 4-dodecyl-2,6-di-tert-butylphenol. In one embodiment the hindered phenol antioxidant may be an ester and may include, e.g., Irganox™ L-135 from BASF GmbH. A more detailed description of suitable ester-containing hindered phenol antioxidant chemistry is found in US Patent 6,559,105.

[0045] The antioxidant may include a substituted hydrocarbyl mono-sulfide represented by Formula 4:

R ⁷ R ⁸

R ⁶ - S - i - i - OH

R ¹⁰ R ⁹ (4) wherein R ⁶ may be a saturated or unsaturated branched or linear alkyl group with 8 to 20 carbon atoms; R ⁷ , R ⁸ , R ⁹ and R ¹⁰ are independently hydrogen or alkyl containing 1 to 3 carbon atoms. In some embodiments the substituted hydrocarbyl monosulfides include n- dodecyl-2-hydroxy ethyl sulfide, l-(tert-dodecylthio)-2-propanol, or combinations thereof. In some embodiments the substituted hydrocarbyl monosulfide is l-(tert-dodecylthio)-2- propanol.

[0046] Anti-foam agents, also known as foam inhibitors, are known in the art and include organic silicones and non-silicon foam inhibitors. Examples of organic silicones include dimethyl silicone and polysiloxanes. Examples of non-silicon foam inhibitors include copolymers of ethyl acrylate and 2-ethylhexylacrylate, copolymers of ethyl acrylate, 2-ethylhexylacrylate and vinyl acetate, polyethers, polyacrylates and mixtures thereof. In some embodiments the anti-foam is a polyacrylate. Antifoams may be present in the composition from 0 to 0.1 wt%, or 0.001 wt % to 0.012 wt %, or 0.004 wt % or even 0.001 wt % to 0.003 wt %.

[0047] Demulsifiers are known in the art and include derivatives of propylene oxide, ethylene oxide, polyoxyalkylene alcohols, alkyl amines, amino alcohols, diamines or polyamines reacted sequentially with ethylene oxide or substituted ethylene oxides or mixtures thereof. Examples of demulsifiers include polyethylene glycols, polyethylene oxides, polypropylene oxides, (ethylene oxide-propylene oxide) polymers and mixtures thereof. In some embodiments the demulsifiers is a polyether. In one embodiment, the demulsifier may be an oxyalkylated phenolic resin blend. Such a blend may comprise formaldehyde polymers with 4-nonylphenol, ethylene oxide and propylene oxide and formaldehyde polymers with 4-nonylphenol ethylene oxide. Demulsifier may be present in the composition from 0 to 0.1 wt% or 0.002 wt % to 0.012 wt%.

[0048] Pour point depressants are known in the art and include esters of maleic anhydride-styrene copolymers, polymethacrylates, polyacrylates, polyacrylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkyl fumarates, vinyl esters of fatty acids, ethylene-vinyl acetate copolymers, alkyl phenol formaldehyde condensation resins, alkyl vinyl ethers and mixtures thereof. In one embodiment, polymethacrylate pour point depressants may be included in amounts of 0 to 0.4 wt% or 0.005 to 0.3 wt% of the hydraulic fluid.

[0049] Metal deactivators may be chosen from derivatives of benzotri azole, 1,2,4- triazole, benzimidazole, 2-alkyldithiobenzimidazole, 2-alkyldithiobenzothiazole, or dimercaptothiadiazole. Examples of such derivatives include 2,5-dimercapto-l,3,4- thiadiazole, or oligomers thereof, a hydrocarbyl -substituted 2,5-dimercapto-l,3,4- thiadiazole, a hydrocarbylthio-substituted 2,5-dimercapto-l,3,4-thiadiazole, or oligomers thereof. The oligomers of hydrocarbyl-substituted 2,5-dimercapto-l,3,4-thiadiazole typically form by forming a sulfur-sulfur bond between 2,5-dimercapto-l,3,4-thiadiazole units to form oligomers of two or more of said thiadiazole units. Examples of a suitable thiadiazole compound include at least one of a dimercaptothiadiazole, 2, 5 -dimercaptofl, 3, 4]-thiadiazole, 3,5-dimercapto-[l,2,4]-thiadiazole, 3,4-dimercapto-[l,2,5]-thiadiazole, or 4-5-dimercapto-[l,2,3]-thiadiazole. Typically, readily available materials such as 2,5-dimercapto-l,3,4-thiadiazole or a hydrocarbyl-substituted 2,5-dimercapto-l,3,4- thiadiazole or a hydrocarbylthio-substituted 2,5-dimercapto-l,3,4-thiadiazole are commonly utilized. In different embodiments the number of carbon atoms on the hydrocarbyl-substituent group includes 1 to 30, 2 to 25, 4 to 20, 6 to 16, or 8 to 10. The 2,5-dimercapto-l,3,4-thiadiazole may be 2,5-dioctyl dithio- 1, 3, 4-thiadiazole, or 2,5-dinonyl dithio- 1, 3, 4-thiadiazole. The metal deactivators may also be described as corrosion inhibitors.

[0050] The metal deactivators may be present in the range from 0 or 0.001 wt % to 0.1 wt %, from 0.01 wt % to 0.04 wt % or from 0.015 wt % to 0.03 wt % of the lubricating oil composition. Metal deactivators may also be present in the composition from 0.002 wt % or 0.004 wt % to 0.02 wt %. The metal deactivator may be used alone or mixtures thereof.

[0051] In one embodiment, the invention provides a hydraulic fluid composition further comprising a metal-containing detergent. In some embodiments, the metal -containing detergent may be a calcium or magnesium detergent. In one embodiment, the metalcontaining detergent may also be an overbased detergent with total base number ranges from 30 to 500 mg KOH/g equivalents. In another embodiment, the metal-containing detergent may be a neutral detergent having a total base number of 0 to 30, or even 0 to 10, or even 30 or lower, or even 10 or lower mg KOH/g equivalents.

[0052] The metal-containing detergent may be chosen from non-sulfur containing phenates, sulfur containing phenates, sulfonates, salixarates, salicylates, and mixtures thereof, or borated equivalents thereof. The detergent may be borated with a borating agent such as boric acid such as a borated overbased calcium or magnesium sulfonate detergent, or mixtures thereof. The detergent may be present at 0 wt % to 5 wt %, or 0.001 wt % to 1.5 wt %, or 0.005 wt % to 1 wt %, or 0.01 wt % to 0.5 wt % of the hydraulic composition.

[0053] In one embodiment, the hydraulic fluid composition of the present invention includes a calcium detergent. In such an embodiment, the calcium detergent may be present in the hydraulic fluid composition in an amount to deliver 5 ppm to 200 ppm or 10 ppm to 150 ppm or 15 ppm to 100 ppm calcium to the hydraulic fluid composition.

[0054] In one embodiment, all of the additives used in the hydraulic fluid composition may be ashless. In another embodiment, the lubricating composition may be free of additives that contain transition metals. In still another embodiment, the lubricating composition may contain additives where calcium is the only metal. [0055] In one embodiment, the lubricant disclosed herein may contain at least one friction modifier. The friction modifier may be present at 0 wt % to 3 wt %, or 0.02 wt % to 2 wt %, or 0.05 wt % to 1 wt %, of the lubricant composition.

[0056] Examples of suitable friction modifiers include long chain fatty acid derivatives of amines, fatty esters, or fatty epoxides; fatty imidazolines such as condensation products of carboxylic acids and polyalkylene-polyamines; amine salts of alkylphosphoric acids; fatty phosphonates; fatty phosphites; borated phospholipids, borated fatty epoxides; glycerol esters; borated glycerol esters; fatty amines; alkoxylated fatty amines; borated alkoxylated fatty amines; hydroxyl and polyhydroxy fatty amines; hydroxy alkyl amides; metal salts of fatty acids; metal salts of alkyl salicylates; fatty oxazolines; fatty ethoxylated alcohols; condensation products of carboxylic acids and polyalkylene polyamines; or reaction products from fatty carboxylic acids with guanidine, aminoguanidine, urea, or thiourea and salts thereof.

[0057] As used herein, the term “fatty alkyl” or “fatty” in relation to friction modifiers means a carbon chain having 8 to 22 carbon atoms, typically a straight carbon chain. Alternatively, the fatty alkyl may be a mono branched alkyl group, with branching typically at the P-position. Examples of mono branched alkyl groups include 2-ethylhexyl, 2- propylheptyl or 2-octyldodecyl.

[0058] The hydraulic fluid composition may also contain one or more viscosity modifiers. Viscosity modifiers (often referred to as viscosity index improvers) suitable for use in the invention include polymeric materials including a styrene-butadiene rubber, an olefin copolymer, a hydrogenated styrene-isoprene polymer, a hydrogenated radical isoprene polymer, a poly(meth)acrylic acid ester, a polyalkylstyrene, a hydrogenated alkenylaryl conjugated-diene copolymer, an ester of maleic anhydride-styrene copolymer or mixtures thereof. In some embodiments the viscosity modifier is a poly(meth)acrylic acid ester, an olefin copolymer or mixtures thereof. The viscosity modifiers may be present at 0 wt % to 10 wt %, 0.5 wt % to 8 wt %, 1 wt % to 6 wt % of the lubricant.

[0059] Exemplary hydraulic fluids may have a formulation as defined the table below. All additives are expressed on an oil-free basis. Example Hydraulic Lubricant compositions

Industrial Application

[0060] In accordance with one aspect of the exemplary embodiment, the hydraulic fluid is for use in a hydraulic system, turbine system or other circulating oil system. The hydraulic system may be a device or apparatus in which the hydraulic fluid transmits energy to different parts of the system by hydraulic force. A turbine lubricant is typically used to lubricate the gears or other moving parts of a turbine (or turbine system), such as a steam turbine or a gas turbine. A circulating oil is typically used to distribute heat to or through a device or apparatus through which it is circulated.

[0061] Viscosity grades generally suitable for hydraulic oils are ISO 10, 15, 22, 32, 46, 68, 100 and 150 (cSt). The viscosity of each grade is the kinematic viscosity at 40 °C +/-10% as measured by ASTM D445 or ISO 3104. As such, an ISO 46 is 46cSt at 40 °C may have a kinematic viscosity of 41.4 - 50.6 cSt at 40 °C. The ISO viscosity classification system is defined in ISO 3448. Exemplary viscosity grades are listed in the table below:

[0062] Accordingly, in some embodiments, the lubricating composition may have an ISO viscosity grade (VG) of 10, 15, 22, 32, 46, 68, 100, 150, 220, 320, 460, or 680 (cSt) grade lubricant. In yet other embodiments, the lubricating composition may have an ISO VG of 68 cSt to 460 cSt or 100 cSt to 420 cSt.

[0063] The present invention provides a method of lubricating a hydraulic system, comprising supplying to said hydraulic system a hydraulic fluid composition as described herein. The present invention also provides a method of operating a hydraulic system, comprising supplying to said hydraulic system a hydraulic fluid composition as described herein. The present invention also includes the use of a hydraulic fluid composition as described herein to lubricate a hydraulic system.

Examples

[0064] Exemplary hydraulic fluid compositions were prepared and evaluated as summarized in the following Examples. All treat rates are oil free (i.e., active) unless otherwise indicated. [0065] A base formulation containing dispersant, ashless antioxidants, ashless phosphorus anti-wear agents, triazole corrosion inhibitors, and other typical hydraulic additives was prepared for top treatment with phosphorus additives of the invention (Table 1).

Table 1 - Base Hydraulic Additive Package ¹

1. Treat rates are oil free unless otherwise indicated

2. Prepared from mid-succan PIB, with poly aromatic poly amine

3. Combination of alkylated diphenylamine and hindered phenol

4. Combination of hydrocarbyl esters of di(C4/C5)dithiophosphoric acid

5. Methy lenebis(dibuty Idithiocarbamate)

6. Combination of alkylated benzotriazole and substituted 1,2,4-triazole

[0066] A series of hydraulic fluid formulations in several ISO viscosity grades were prepared to evaluate demulsibility and corrosion resistance. Example formulations were prepared by top-treating fully formulated hydraulic fluids with additives to be evaluated (Table 2). Treat rate of the amine phosphate was also varied.

Table 2 - Hydraulic Lubricant Compositions

1. Treat rates are oil free unless otherwise indicated

2. Group II base oil with kinematic viscosity at 100 °C of 12 cSt

3. Group II base oil with kinematic viscosity at 100 C of 11.5 cSt

4. Group II base oil with kinematic viscosity at 100 °C of 6.4 cSt

5. Group I bright stock with kinematic viscosity at 100 °C of 32 cSt

6. Mixed salt of 2-ethylhexylamine with combination of mono- and di-(iso-octyl) phosphoric acid 7. Mixed salts of C12-14-t-alkyl(mono)amine with combination of mono- and di-(C14-18 fatty alkyl) phosphoric acid

[0067] The impact of the formulating components at various concentrations was also evaluated. The base formulation was varied in its treat rate, and amine phosphate additive of the invention was top-treated (Table 3).

Table 3 - Hydraulic Lubricating Compositions

1. Treat rates are oil free unless otherwise indicated

2. Group II base oil with kinematic viscosity at 100 °C of 12 cSt

3. Group II base oil with kinematic viscosity at 100 C of 11.5 cSt

4. Group I bright stock with kinematic viscosity at 100 °C of 32 cSt

5. Mixed salt of 2-ethylhexylamine with combination of mono- and di-(iso-octyl) phosphoric acid

[0068] Lubricant formulations are evaluated for protecting hydraulic systems, with particular emphasis on wear protection, corrosion protection, and demulsibility. Corrosion (or rust) prevention is evaluated in the Mineral Oil Rust Prevention test, carried out according to ASTM D665B. Demulsibility is determined via several tests, including the Standard Test Method for Water Separability of Petroleum Oils and Synthetic Fluids (according to ASTM D1401) and the Demulsibility Characteristics of Lubricating Oils test

(according to ASTM D2711 Procedure B). Results of testing are summarized below (Table 4).

Table 4 - Demulsibility Testing

1. Average of 2 tests

2. Average of 3 tests Table 4 (cont’d)

[0069] The data demonstrates the addition of amine phosphate to the lubricating compositions resulted in increased demulsibility, /.< ., more rapid reduction in emulsion volume. This phenomenon was demonstrated in multiple viscosity grades at different treat rates of the additive.

[0070] As used herein, “substantially free” means that the amount of the material in question is less than an amount that will affect the relevant performance of the fluid in a measurable way. “Substantially free” may also mean that the material in question is not intentionally added to the composition but does not exclude the presence of such material as contaminants. “Substantially free” may also mean that the material in question may be present in amounts lower than the detection limit of standard test methods now known to those skilled in the art or hereafter developed. In some embodiments, “substantially free” may mean less than 10 ppm by weight or even less than 5 ppm by weight.

[0071] It is known that some of the materials described above may interact in the final formulation, so that the components of the final formulation may be different from those that are initially added. The products formed thereby, including the products formed upon employing lubricant composition of the present invention in its intended use, may not be susceptible of easy description. Nevertheless, all such modifications and reaction products are included within the scope of the present invention; the present invention encompasses lubricant composition prepared by admixing the components described above.

[0072] Each of the documents referred to above is incorporated herein by reference. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word “about.” Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, byproducts, derivatives, and other such materials which are normally understood to be present in the commercial grade. However, the amount of each chemical component is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, unless otherwise indicated. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention may be used together with ranges or amounts for any of the other elements.

[0073] While the invention has been explained in relation to its preferred embodiments, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. Therefore, it is to be understood that the invention disclosed herein is intended to cover such modifications as fall within the scope of the appended claims.