Lubricating composition

Abstract

A substantially zinc-free hydraulic fluid is provided. The substantially zinc-free hydraulic fluid contains a calcium detergent, an ashless antioxidant, and a metal-free phosphorus-containing antiwear agent. In one embodiment, the fluid contains at least 90% by weight of a base oil having less than 500 ppm sulfur, a calcium detergent in an amount to deliver 5 ppm to 200 ppm calcium to the fluid, at least one metal-free phosphorus-containing antiwear agent to provide 10 ppm to 150 ppm phosphorus, and one or more ashless antioxidants. A method of lubricating a hydraulic system using a substantially zinc-free fluid is also provided.

Description

[0001] The present invention relates to low zinc hydraulic fluid compositions capable of providing wear protection in hydraulic systems. Background Art

[0002] Hydraulic systems rely on hydraulic fluid under pressure to create motion in machine components. Pumps are used to create a combination of flow and pressure in hydraulic systems. Hydraulic fluid can be used in such systems to provide pressurized fluid. While the primary purpose of hydraulic fluid is to transfer energy (power) from a source (pump) to an end use (motor, cylinder, etc.), hydraulic fluid provides lubrication, thereby helping to minimize wear, reduce friction, provide cooling, inhibit corrosion, and minimize deposits, thereby extending the life and efficiency of the system.

[0003] Due to environmental concerns and potential toxicity issues, there is an increasing interest in lubricating compositions containing ashless additives. In some applications, the use of anti-wear additives such as ZDDP is reduced in favor of other ashless additives. Therefore, for hydraulic systems, there is a need to provide hydraulic fluid compositions containing ashless additives while still providing anti-wear performance that is at least as good as or even better than zinc-containing additives. The present invention can also be used to reduce leakage in high pressure hydraulic systems. Summary of the invention

[0004] The present invention provides a hydraulic fluid. The hydraulic fluid of the present invention comprises a base oil, a calcium detergent, a metal-free phosphorus-containing antiwear agent and an ashless antioxidant, wherein the composition is substantially free of zinc.

[0005] In one embodiment, the hydraulic fluid comprises (a) at least 90 weight percent of a base oil having less than 500 ppm sulfur, (b) a calcium detergent in an amount sufficient to deliver 5 ppm to 200 ppm, or 5 ppm to 150 ppm, or 5 ppm to 100 ppm calcium to the fluid, (c) at least one metal-free phosphorus-containing antiwear agent, and (d) one or more ashless antioxidants, wherein the hydraulic fluid has 10 ppm to 150 ppm phosphorus and wherein the hydraulic fluid is substantially free of zinc.

[0006] The present invention also includes a method of lubricating a hydraulic system, the method comprising supplying to the hydraulic system a hydraulic fluid composition comprising (a) at least 90 weight percent of a base oil having less than 500 ppm sulfur, (b) a calcium detergent in an amount sufficient to deliver 5 ppm to 200 ppm, or 5 ppm to 150 ppm, or 5 ppm to 100 ppm calcium to the fluid, (c) at least one metal-free phosphorus-containing antiwear agent, and (d) one or more ashless antioxidants, wherein the hydraulic fluid has 10 ppm to 150 ppm phosphorus and wherein the hydraulic fluid is substantially free of zinc.

[0007] The present invention also includes the use of a hydraulic fluid for lubricating a hydraulic system, the hydraulic fluid comprising (a) at least 90 weight percent of a base oil having less than 500 ppm sulfur, (b) a calcium detergent in an amount sufficient to deliver 5 ppm to 200 ppm, or 5 ppm to 150 ppm, or 5 ppm to 100 ppm calcium to the fluid, (c) at least one metal-free phosphorus-containing antiwear agent, and (d) one or more ashless antioxidants, wherein the hydraulic fluid has 10 ppm to 150 ppm phosphorus and wherein the hydraulic fluid is substantially free of zinc.

[0008] The components and applications of the present invention will be described in more detail in the specific embodiments of the present invention. DETAILED DESCRIPTION

[0009] The present invention provides a hydraulic fluid composition as described herein comprising a base oil, a calcium detergent, at least one metal-free phosphorus-containing antiwear agent and one or more ashless antioxidants. Preferably, the hydraulic fluid is substantially free of zinc.

[0010] Oil of lubricating viscosity

[0011] One component of the disclosed invention is a base oil. The base oil can be selected from any of the base oils in Group IV of the American Petroleum Institute (API) Base Oil Interchangeability Guide, i.e.

[0012]

[0013] Class I, Class II and Class III are mineral oil base stocks. The oil with lubricating viscosity can include natural or synthetic oils and mixtures thereof. A mixture of mineral oil and synthetic oil can be used, for example polyalphaolefin oil and / or polyester oil.

[0014] Natural oils include animal and vegetable oils (e.g., vegetable acid esters) and mineral lubricating oils, such as liquid petroleum and solvent-treated or acid-treated paraffinic, cycloparaffinic or mixed paraffinic-cycloparaffinic types. Hydrotreated or hydrocracked oils are also suitable oils of lubricating viscosity. Oils of lubricating viscosity derived from coal or shale are also suitable.

[0015] Synthetic oils include hydrocarbon oils and halogen-substituted hydrocarbon oils, such as polymerized and interpolymerized olefins and mixtures thereof, alkylbenzenes, polyphenyls, alkylated diphenyl ethers and alkylated diphenyl sulfides and derivatives, analogs and homologs thereof. Alkylene oxide polymers and interpolymers and derivatives thereof, and materials wherein the terminal hydroxyl groups have been modified by, for example, esterification or etherification are other types of synthetic lubricating oils. Other suitable synthetic lubricating oils include esters of dicarboxylic acids and esters made from C5 to C12 monocarboxylic acids and polyols or polyol ethers. Other synthetic lubricating oils include liquid esters of phosphorus-containing acids, polymerized tetrahydrofuran, silicon-based oils, such as polyalkyl-siloxane oils, polyaryl-siloxane oils, polyalkoxy-siloxane oils or polyaryloxy-siloxane oils and silicate oils.

[0016] Other synthetic oils include those produced by the Fischer-Tropsch reaction, typically hydroisomerizing Fischer-Tropsch hydrocarbons or waxes. In one embodiment, the oil may be made by a Fischer-Tropsch gas-to-liquid synthesis procedure as well as other gas-to-liquid oils.

[0017] Natural or synthetic unrefined, refined and re-refined oils (and mixtures thereof) of the types disclosed above may be used. Unrefined oils are oils obtained directly from natural or synthetic sources without further purification treatment. Refined oils are similar to unrefined oils, except that the refined oils have been further treated in one or more purification steps to improve one or more properties. Re-refined oils are obtained by methods similar to those used to obtain refined oils, applied to refined oils already in service. Re-refined oils typically require additional processing to remove spent additives and oil breakdown products.

[0018] In some embodiments, the industrial lubricant composition may also include a small amount of one or more non-synthetic base oils. Examples of these non-synthetic base oils include any of the base oils described herein, including API Group I, Group II, or Group III base oils.

[0019] The amount of oil of lubricating viscosity present is typically the remainder remaining after subtracting the sum of the amounts of the compound of the invention and other performance additives from 100 wt%. The oil of lubricating viscosity may be present in a major amount for a lubricating composition, or in an amount formed from a concentrate for a concentrate and / or additive composition. The industrial lubricant composition of the present invention may be a lubricant composition or a concentrate and / or additive composition.

[0020] In a fully formulated lubricating oil composition according to the present invention, the oil of lubricating viscosity is usually present in a major amount (i.e., an amount greater than 50% by weight). Typically, the oil of lubricating viscosity is present in an amount of 75% to 98% by weight of the total composition, and usually greater than 80% or even 90% by weight.

[0021] The various oils of lubricating viscosity described can be used alone or in combination. The oil of lubricating viscosity (considering all oils present) can be used in the described industrial lubricant composition in a range of about 40 wt % or 50 wt % to about 99 wt %, or a minimum of 50 wt %, 70 wt %, 80 wt %, 90 wt % or even 97 wt % to a maximum of 98 wt %, 98.5 wt %, 99 wt % or even 99.8 wt %.

[0022] In a concentrate composition, typically the amounts of additives and other components remain the same, but the amount of oil of lubricating viscosity is reduced in order to make the composition more concentrated and more efficiently stored and / or transported. One skilled in the art will be able to readily adjust the amount of oil of lubricating viscosity present to provide a concentrate and / or additive composition.

[0023] In one embodiment of the invention, the base oil used in the hydraulic fluid of the invention will contain less than 1000 ppm by weight, or even less than 750 ppm by weight, or even less than 500 ppm by weight of sulfur.

[0024] Calcium detergent

[0025] The hydraulic fluid of the present invention also contains a metal-containing detergent. In some embodiments, the metal-containing detergent can be a calcium or magnesium detergent. In one embodiment, the metal-containing detergent includes or consists of a calcium detergent. In one embodiment, the metal-containing detergent can be a neutral detergent or a high-alkaline detergent. The high-alkaline detergent can have a total base number (TBN) of 80 mg KOH / g to 300 mg KOH / g. The neutral detergent has a total base number (TBN) of 10 mg KOH / g or less or even 5 mg KOH / g or less, such as 0 mg KOH / g, 1 mg KOH / g, 2 mg KOH / g, 3 mg KOH / g or 4 mg KOH / g. In another embodiment, the metal-containing detergent includes or consists of a neutral calcium detergent.

[0026] The metal-containing detergent may be selected from non-sulfur-containing phenates, sulfur-containing phenates, sulfonates, salicylates, salicylates, and mixtures thereof. In one embodiment, the metal-containing detergent is a calcium detergent selected from calcium phenate, calcium sulfonate, calcium salicylate, calcium salicylate, and mixtures thereof.

[0027] In one embodiment, the metal-containing detergent for the hydraulic fluid of the present invention comprises an alkylated aromatic sulfonate. The sulfonate detergent may be prepared from a mono- or di-hydrocarbyl-substituted benzene (or toluene, naphthalene, indenyl, indanyl or dicyclopentadienyl) sulfonic acid, wherein the hydrocarbyl group may contain 6 to 40, or 8 to 35, or 9 to 20 carbon atoms. The hydrocarbyl group may be derived from polypropylene or a straight or branched alkyl group containing at least 10 carbon atoms. Examples of suitable alkyl groups include branched and / or straight chain decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, octadecenyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl or mixtures thereof. In one embodiment, the hydraulic fluid of the present invention contains a neutral calcium salt of an alkylated benzene sulfonic acid. In another embodiment, the detergent comprises a neutral calcium salt of an alkylated naphthalene sulfonic acid. In another embodiment, the detergent comprises a neutral calcium salt of an alkylated toluene sulfonic acid. In another embodiment, the alkyl group of the alkylated sulfonic acid detergent contains from 6 to 20 carbon atoms.

[0028] In one embodiment, the hydraulic fluid of the present invention contains a calcium detergent as described herein in an amount sufficient to deliver 5 ppm to 200 ppm, or even 10 ppm to 150 ppm, or even 20 ppm to 100 ppm by weight of calcium to the hydraulic fluid.

[0029] Phosphorus antiwear agent

[0030] In one embodiment, the hydraulic fluid of the present invention comprises at least one metal-free phosphorus antiwear agent. Examples of suitable antiwear agents include tartrates, tartrimides, oil-soluble amine salts of phosphorus compounds; sulphurized olefins; phosphites (such as dibutyl phosphite or dioleyl phosphite); phosphonates; compounds containing thiocarbamates, such as thiocarbamates, thiocarbamates, thiocarbamates, methyl thiocarbamates, alkylene-coupled thiocarbamates, bis(S-alkyldithiocarbamoyl) disulfides and oil-soluble phosphorus amine salts. In one embodiment, the metal-free phosphorus antiwear agent comprises or consists of (thio)phosphates. As used herein, the term (thio)phosphate is understood to include phosphates, thiophosphates or mixtures thereof.

[0031] The phosphorus compound that can be used in the present invention may include a triaryl phosphate or a triaryl thiophosphate represented by the following formula (1):

[0032]

[0033] In formula (1), R is a hydrogen atom or an alkyl group having 3 to 9 (e.g., 3, 4, 5, 6, 7, 8, 9) carbon atoms or a combination of carbon atoms thereof, and X is an oxygen atom or a sulfur atom. In formula (1), the three R groups may be the same or different from each other. Examples of alkyl groups having 4 or fewer carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl.

[0034] Examples of the phosphorus compound represented by formula (1) include triphenyl phosphate, tricresyl phosphate, triphenyl thiophosphate, tricresyl thiophosphate, and butylated triphenyl thiophosphate.

[0035] Another example of the phosphorus compound that can be used in the present invention is represented by the following formula (2).

[0036]

[0037] In formula (2), R1 represents a linear or branched alkylene group having 1 to 8 carbon atoms, R2 and R3 each represent a hydrocarbon group having 3 to 20 carbon atoms, and X 2 and X 3 Each independently represents an oxygen atom or a sulfur atom.

[0038] In one embodiment, R1 can be a straight chain or branched chain alkylene group having 1 to 8 carbon atoms, more preferably a straight chain or branched chain alkylene group having 2 to 4 carbon atoms, and further preferably a branched chain alkylene group. Specifically, R1 is preferably, for example, -CH2CH2-, -CH2CH(CH3)-, -CH2CH(CH2CH3)-, or -CH2CH(CH2CH2CH3)-, and more preferably -CH2CH(CH3)- or -CH2CH(CH3)CH2-.

[0039] In one embodiment, R2 to R3 each preferably represents 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, R2 to R3 each preferably is selected from the group consisting of propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl, hexyl, 2-ethylbutyl, 1-methylpentyl, 1,3-dimethylbutyl and 2-ethylhexyl.

[0040] In one embodiment, X 2 and X 3 In another embodiment, X 2 and X 3 In another embodiment, X 2 is oxygen and X 3 is sulfur, and in another embodiment, X 2 is sulfur and X 3For oxygen.

[0041] Another phosphorus compound that can be used in the present invention includes a phosphorothioate compound represented by the following formula (3).

[0042]

[0043] In formula (3), R 4 , R 5 and R 7 Each is 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. 6 is a straight or branched alkylene group having 1 to 8 carbon atoms, X 4 and X 5 Each is independently an oxygen atom or a sulfur atom. In one embodiment of formula (3), at least one sulfur atom is present.

[0044] In one embodiment, X 4 and X 5 In another embodiment, X 4 and X 5 In another embodiment, X 4 is oxygen and X 5 is sulfur, and in another embodiment, X 4 is sulfur and X 5 For oxygen.

[0045] In one embodiment, the metal-free antiwear agent of the present invention may be selected from methyl 3-((dialkoxythiophosphoryl)thio)propanoate, 3-((diisobutoxythiophosphoryl)thio)-2-methylpropanoic acid and mixtures thereof having mixed C4 / C5 alkoxy groups.

[0046] The hydraulic fluids of the present invention will contain from 10 ppm to 200 ppm by weight phosphorus or even from 20 ppm to 150 ppm by weight phosphorus.If the antiwear agent is the only phosphorus containing compound present in the hydraulic fluid, such compound will be present in an amount sufficient to deliver the desired amount of phosphorus.

[0047] Antioxidants

[0048] The hydraulic fluid of the present invention also contains at least one ashless antioxidant. In some embodiments, the hydraulic fluid comprises at least one ashless antioxidant selected from a hindered phenol ester antioxidant, an alkylated diarylamine antioxidant, or a mixture thereof. The antioxidant may be present in an amount of 0% to 4.0% by weight of the lubricant, or 0.02% to 3.0% by weight, or 0.03% to 1.5% by weight, or 0.05% to 0.5% by weight.

[0049] In some embodiments, the lubricant composition may further include at least one ashless antioxidant. Suitable antioxidants include phenolic antioxidants, which may be represented by the general formula (IV):

[0050]

[0051] Where R 5 is an alkyl group containing 1 to 24, or 4 to 18 carbon atoms, and a is an integer from 1 to 5, or from 1 to 3, or 2. Phenol may be a butyl-substituted phenol containing 2 or 3 tert-butyl groups, such as the phenol in formula (V):

[0052]

[0053] The para position may also be occupied by a hydrocarbyl group or a group bridging two aromatic rings. In certain embodiments, the para position is occupied by an ester-containing group, such as, for example, an antioxidant of formula (VI):

[0054]

[0055] Where R 6 is a hydrocarbyl group, such as an alkyl group containing, for example, 1 to 18, or 2 to 12, or 2 to 8, or 2 to 6 carbon atoms; and the tertiary alkyl group may be a tert-butyl group. Such antioxidants are described in more detail in US Pat. No. 6,559,105.

[0056] In some embodiments, the antioxidant may include a hindered phenol. Examples of suitable hydrocarbyl groups of the hindered phenol include, but are not limited to, 2-ethylhexyl or n-butyl esters, dodecyl, or mixtures thereof. Examples of methylene-bridged hindered phenols include, but are not limited to, 4,4'-methylene-bis(6-tert-butyl-o-cresol), 4,4'-methylene-bis(2-tert-amyl-o-cresol), 2,2'-methylene-bis(4-methyl-6-tert-butylphenol), 4,4'-methylene-bis(2,6-di-tert-butylphenol), or mixtures thereof.

[0057] Antioxidants also include aromatic amines, such as those of formula (VII):

[0058]

[0059] Where R 7 It may be an aryl group, such as a phenyl group, a naphthyl group or a 9 substituted phenyl group, and R 8 and R 9 may independently be hydrogen or an alkyl group containing 1 to 24, or 4 to 20, or 6 to 12 carbon atoms. In one embodiment, the aromatic amine antioxidant may include an alkylated diphenylamine, such as nonylated diphenylamine of formula (VIII):

[0060]

[0061] or a mixture of dinonylated diphenylamine and monononylated diphenylamine.

[0062] Other additives

[0063] The hydraulic fluid compositions of the present invention may be in the form of concentrates and / or fully formulated lubricants. If the hydraulic fluids of the present invention (including the additives disclosed herein) are in the form of concentrates that can be combined with additional oils to form all or part of a finished lubricant, the ratio of these additives to the oil of lubricating viscosity and / or diluent oil includes a range of 1:99 to 99:1 by weight or 80:20 to 10:90 by weight.

[0064] In addition to the above specific additives, the hydraulic fluid composition may also contain one or more additional other additives. In some embodiments, the additional additives may include corrosion inhibitors, rust inhibitors, foam inhibitors, surfactants, dispersants, demulsifiers, metal deactivators, friction modifiers, emulsifiers, extreme pressure agents, pour point depressants, viscosity modifiers, or any combination thereof.

[0065] In one embodiment, the fluid of the present invention contains a surfactant. In one embodiment, the surfactant is an ashless surfactant. Suitable surfactants may include substituted polyisobutylene compounds. For example, useful surfactants may include (i) polyetheramines; (ii) succinimide dispersants; (iii) Mannich reaction products of dialkylamines, aldehydes and hydrocarbyl-substituted phenols; or any combination thereof. In some embodiments, the dispersant may be present at 0 wt % or 0.01 wt % to 2.0 wt %, 0.025 wt % to 1.5 wt %, or 0.05 wt % to 1 wt %, or 0.05 wt % to 0.5 wt % of the total composition. In an exemplary embodiment, the hydraulic fluid contains 0.025 wt % to 0.075 wt % of a surfactant.

[0066] The surfactant used in the present invention may also include one or more dispersants. Dispersants that may be included in the composition include those having an oil-soluble polymeric hydrocarbon backbone and having functional groups that can associate with the particles to be dispersed. The weight average molecular weight of the polymeric hydrocarbon backbone may range from 750 daltons to 1500 daltons. Exemplary functional groups include amine, alcohol, amide, and ester polar moieties, which are typically connected to the polymer backbone via a bridging group. Exemplary dispersants include the Mannich dispersants described in U.S. Pat. Nos. 3,697,574 and 3,736,357; the ashless succinimide dispersants described in U.S. Pat. Nos. 4,234,435 and 4,636,322; the amine dispersants described in U.S. Pat. Nos. 3,219,666, 3,565,804, and 5,633,326; the Koch dispersants described in U.S. Pat. Nos. 5,936,041, 5,643,859, and 5,627,259; and the polyalkylene succinimide dispersants described in U.S. Pat. Nos. 5,851,965, 5,853,434, and 5,792,729.

[0067] In one embodiment, the surfactant comprises polyisobutenyl succinimide, polyisobutenyl succinimide derived from aromatic polyamines, or mixtures thereof.

[0068] Defoamers, also known as foam inhibitors, are known in the art and include organosiloxanes and non-silicone foam inhibitors. Examples of organosiloxanes include dimethylsiloxanes and polysiloxanes. Examples of non-silicone foam inhibitors include copolymers of ethyl acrylate and 2-ethylhexyl acrylate; copolymers of ethyl acrylate, 2-ethylhexyl acrylate and vinyl acetate; polyethers; polyacrylates and mixtures thereof. In some embodiments, the defoamer is a polyacrylate. The defoamer may be present in the composition at 0.001 wt % to 0.012 wt %, or 0.004 wt %, or even 0.001 wt % to 0.003 wt %.

[0069] Demulsifier is known in the art and includes derivatives of propylene oxide, ethylene oxide, polyoxyalkylene alcohol, alkylamine, amino alcohol, diamine or polyamines reacted continuously with ethylene oxide or substituted ethylene oxide or its mixture. The example of demulsifier includes polyethylene glycol, polyethylene oxide, polypropylene oxide, (ethylene oxide-propylene oxide) polymer and their mixture. In some embodiments, demulsifier is polyether. In one embodiment, demulsifier can be an alkoxylated phenolic resin blend. This blend can include formaldehyde polymers with 4-nonylphenol, ethylene oxide and propylene oxide and formaldehyde polymers with 4-nonylphenol ethylene oxide. Demulsifier can be present in the composition at 0.002 weight % to 0.012 weight %.

[0070] Pour point depressants are known in the art and include esters of maleic anhydride-styrene copolymers, polymethacrylates; polyacrylates; polyacrylamides; condensation products of halogenated paraffins and aromatic compounds; carboxylic acid vinyl ester polymers; and terpolymers of dialkyl fumarates, vinyl esters of fatty acids, ethylene-vinyl acetate copolymers, alkylphenol formaldehyde condensation resins, alkyl vinyl ethers, and mixtures thereof.

[0071] The hydraulic fluid composition may further comprise a rust inhibitor. Suitable rust inhibitors include hydrocarbylamine salts of alkylphosphoric acids, hydrocarbylamine salts of dialkyldithiophosphoric acids, hydrocarbylamine salts of hydrocarbylarylsulfonic acids, fatty carboxylic acids or esters thereof, esters of nitrogen-containing carboxylic acids, ammonium sulfonates, imidazolines, alkylated succinic acid derivatives reacted with alcohols or ethers, or any combination thereof; or mixtures thereof.

[0072] Suitable hydrocarbyl amine salts of alkyl phosphoric acids can be represented by the following formula:

[0073]

[0074] Where R 26 and R 27 are independently hydrogen, an alkyl chain or a hydrocarbon group, typically R 26 and R 27 At least one of R is a hydrocarbon group. 26 and R 27 Contains 4 to 30, or 8 to 25, or 10 to 20, or 13 to 19 carbon atoms. 28 , R 29 and R 30 R is independently hydrogen, an alkyl branched or straight chain having 1 to 30, or 4 to 24, or 6 to 20, or 10 to 16 carbon atoms. 28 , R 29 and R 30 are independently hydrogen, a branched or straight alkyl chain, or R 28 , R 29 and R 30 At least one or both of them are hydrogen.

[0075] Applicable to R 28 , R 29 and R 30 Examples of alkyl groups 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.

[0076] In one embodiment, the hydrocarbyl amine salt of an alkyl phosphoric acid is C14 To C 18 Alkylated phosphoric acid 81R (produced and sold by Rohm and Haas), the 81R is C 11 To C 14 A mixture of tertiary alkyl primary amines.

[0077] Hydrocarbylamine salts of dialkyl dithiophosphoric acids may include rust inhibitors such as hydrocarbylamine salts of dialkyl dithiophosphoric acids. These may be heptyl or octyl or nonyl dithiophosphoric acids with ethylenediamine, morpholine or 81R or a mixture thereof.

[0078] The hydrocarbyl amine salt of a hydrocarbyl aryl sulfonic acid may include the ethylenediamine salt of dinonylnaphthalene sulfonic acid.

[0079] Examples of suitable fatty carboxylic acids or esters thereof include glycerol monooleate and oleic acid.

[0080] The rust inhibitor may be present in a range of 0 wt % or 0.02 wt % to 0.2 wt %, 0.03 wt % to 0.15 wt %, 0.04 wt % to 0.12 wt % or 0.05 wt % to 0.1 wt % of the lubricating oil composition. The rust inhibitor may be used alone or in a mixture thereof.

[0081] The hydraulic fluid may also contain a metal deactivator. The metal deactivator may be selected from a derivative of benzotriazole, 1,2,4-triazole, benzimidazole, 2-alkyldithiobenzimidazole, 2-alkyldithiobenzothiazole or dithiothiadiazole. Examples of such derivatives include 2,5-dithio-1,3,4-thiadiazole or oligomers thereof, hydrocarbyl-substituted 2,5-dithio-1,3,4-thiadiazole, hydrocarbylsulfur-substituted 2,5-dithio-1,3,4-thiadiazole or oligomers thereof. Hydrocarbyl-substituted 2,5-dithio-1,3,4-thiadiazole oligomers are generally formed by forming sulfur-sulfur bonds between 2,5-dithio-1,3,4-thiadiazole units to form oligomers of two or more of the thiadiazole units. Examples of suitable thiadiazole compounds include at least one of dimercaptothiadiazole, 2,5-dimercapto-[1,3,4]-thiadiazole, 3,5-dimercapto-[1,2,4]-thiadiazole, 3,4-dimercapto-[1,2,5]-thiadiazole or 4-5-dimercapto-[1,2,3]-thiadiazole. Generally, readily available materials such as 2,5-dimercapto-1,3,4-thiadiazole or hydrocarbyl-substituted 2,5-dimercapto-1,3,4-thiadiazole or hydrocarbylsulfide-substituted 2,5-dimercapto-1,3,4-thiadiazole are generally utilized. In various 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-1,3,4-thiadiazole can be 2,5-dioctyldithio-1,3,4-thiadiazole or 2,5-dinonyldithio-1,3,4-thiadiazole. Metal deactivators can also be described as corrosion inhibitors.

[0082] The metal deactivator may be present in the lubricating oil composition at 0 wt % or in a range of 0.001 wt % to 0.1 wt %, 0.01 wt % to 0.04 wt %, or 0.015 wt % to 0.03 wt %. The metal deactivator may also be present in the composition at 0.002 wt % or 0.004 wt % to 0.02 wt %.

[0083] In one embodiment, the hydraulic fluids 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.

[0084] As used herein, the term "fatty alkyl" or "fat" with respect to friction modifiers refers to a carbon chain having 8 to 22 carbon atoms, typically a straight carbon chain. Alternatively, the fatty alkyl group may be a monobranched alkyl group, wherein the branching is typically at the beta position. Examples of monobranched alkyl groups include 2-ethylhexyl, 2-propylheptyl, or 2-octyldodecyl.

[0085] Examples of suitable friction modifiers include long chain fatty acid derivatives of amines, fatty acid esters or fatty epoxides; fatty imidazolines, such as condensation products of carboxylic acids and polyalkylene polyamines; amine salts of alkyl phosphoric acids; fatty phosphonates; fatty phosphites; borated phospholipids, borated fatty epoxides; glycerides; borated glycerides; fatty amines; alkoxylated fatty amines; borated alkoxylated fatty amines; hydroxy and polyhydroxy fatty amines; hydroxyalkylamides; 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 of fatty carboxylic acids with guanidine, aminoguanidine, urea or thiourea and their salts.

[0086] The hydraulic fluid may also contain one or more viscosity modifiers. Any known viscosity modifier may be used. In one embodiment, the lubricating composition of the present invention is substantially free of or completely free of poly (meth) acrylate as a viscosity modifier. Viscosity modifiers suitable for the present invention (commonly referred to as viscosity index improvers) include polymeric materials, which include esters of styrene-butadiene rubber, olefin copolymers, hydrogenated styrene-isoprene polymers, hydrogenated free radical isoprene polymers, poly (meth) acrylates, polyalkyl styrenes, hydrogenated alkenyl aryl conjugated diene copolymers, maleic anhydride-styrene copolymers or mixtures thereof. In some embodiments, the viscosity modifier is poly (meth) acrylate, olefin copolymers or mixtures thereof. The viscosity modifier may be present in 0% to 10% by weight, 0.5% to 8% by weight, 1% to 6% by weight of the lubricant.

[0087] In one embodiment, all additives used in the lubricating composition may be ashless. In another embodiment, the lubricating composition may be free of additives containing transition metals. In yet another embodiment, the lubricating composition may contain additives in which calcium is the only metal.

[0088] Industrial Applications

[0089] According to one aspect of the exemplary embodiment, the hydraulic fluid is used in a hydraulic system, a turbine system, or other circulating oil system. A hydraulic system may be a device or apparatus in which a hydraulic fluid transfers energy to different parts of a system by hydraulic force. Turbine lubricants are typically used to lubricate gears or other moving parts of a turbine (such as a steam turbine or a gas turbine) (or a turbine system). Circulating oils are typically used to distribute heat to or through a device or apparatus that circulates it.

[0090] Viscosity grades commonly used 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. Thus, an ISO 46 of 46 cSt at 40°C may have a kinematic viscosity of 41.4 cSt to 50.6 cSt at 40°C. The ISO viscosity classification system is defined in ISO 3448. Exemplary viscosity grades are listed in the following table:

[0091]

[0092] Thus, in some embodiments, the lubricating composition may have a lubricant with an ISO viscosity grade (VG) of 10, 15, 22, 32, 46, 68, 100, or 150 (cSt). In other embodiments, the lubricating composition may have an ISO VG of 22 cSt, 32 cSt, 46 cSt, or 68 cSt. According to one aspect of an exemplary embodiment, a method for providing reduced sludge formation in a hydraulic system may include supplying an exemplary hydraulic fluid to the hydraulic system.

[0093] The present invention includes a hydraulic fluid having an ISO viscosity grade of 22 cSt or 32 cSt or 46 cSt or 68 cSt and comprising (a) at least 90 weight percent of a base oil having less than 500 ppm sulfur, (b) a calcium detergent in an amount sufficient to deliver 5 ppm to 200 ppm, or 5 ppm to 150 ppm, or 5 ppm to 100 ppm of calcium to the fluid and less than 10 mg of KOH / g TBN, wherein the calcium detergent comprises or consists of a neutral or overbased alkylated aromatic sulfonate containing a linear or branched alkyl group containing 6 to 20 carbon atoms, (c) at least one metal-free phosphorus antiwear agent comprising or consisting of a (thio)phosphate ester, and (d) 0.02 wt % to 3.0 wt %, or 0.03 wt % to 1.5 wt %, or 0.05 wt % to 0.5 wt % of one or more ashless antioxidants, wherein the hydraulic fluid has 10 ppm to 150 ppm phosphorus, and wherein the hydraulic fluid contains less than 10 ppm or even less than 5 ppm zinc. In one embodiment, the calcium detergent further comprises an alkylated naphthalenesulfonic acid, a calcium phenate detergent, a calcium salicylate detergent, or a calcium salicylate detergent. The hydraulic fluid described in this paragraph also contains 0.025 wt % to 0.75 wt % of an ashless surfactant comprising or consisting of an ashless polyisobutylene-based surfactant, such as a polyisobutylene-based succinimide derived from an aromatic polyamine.

[0094] The present invention also includes a hydraulic fluid having an ISO viscosity grade of 22 cSt or 32 cSt or 46 cSt or 68 cSt and comprising (a) at least 90 wt% of a base oil having less than 500 ppm sulfur, (b) a calcium detergent in an amount sufficient to deliver 5 ppm to 200 ppm, or 5 ppm to 150 ppm, or 5 ppm to 100 ppm calcium to the fluid and a TBN of less than 10 mg KOH / g, wherein the calcium detergent comprises or consists of a neutral salt of an alkylated naphthalene sulfonic acid, (c) at least one metal-free phosphorus-containing antiwear agent comprising or consists of a (thio)phosphate ester, and (d) 0.02 wt% to 3.0 wt%, or 0.03 wt% to 1.5 wt%, or 0.05 wt% to 0.5 wt% of one or more ashless antioxidants, wherein the hydraulic fluid has 10 ppm to 150 ppm phosphorus, and wherein the hydraulic fluid contains less than 10 ppm or even less than 5 ppm zinc. In one embodiment, the calcium detergent also includes a neutral or overbased alkylated aromatic sulfonate (the neutral or overbased alkylated aromatic sulfonate contains a straight or branched alkyl group containing 6 to 20 carbon atoms), a calcium phenate detergent, a calcium salicylate detergent, or a calcium salicylate detergent. The hydraulic fluid described in this paragraph also contains 0.025 wt % to 0.75 wt % of an ashless surfactant, the ashless surfactant including or consisting of an ashless polyisobutylene-based surfactant, such as a polyisobutylene-based succinimide derived from an aromatic polyamine.

[0095] The present invention also provides a method of lubricating a hydraulic system, wherein the method comprises supplying a hydraulic fluid as described herein to the hydraulic system.

[0096] In one embodiment, the present invention provides a method of lubricating a hydraulic system, the method comprising supplying to the hydraulic system a hydraulic fluid composition having an ISO viscosity grade of 22 cSt or 32 cSt or 46 cSt or 68 cSt and comprising (a) at least 90 wt. % of a base oil having less than 500 ppm sulfur, (b) a calcium detergent in an amount sufficient to deliver 5 ppm to 200 ppm, or 5 ppm to 150 ppm, or 5 ppm to 100 ppm of calcium to the fluid and less than 10 mg of % or less than 5 ppm of zinc; and (e) 0.025 wt % to 0.75 wt % of an ashless surfactant comprising or consisting of an ashless polyisobutylene-based surfactant, such as a polyisobutylene-based succinimide derived from an aromatic polyamine.

[0097] In another embodiment, the present invention provides a method of lubricating a hydraulic system, the method comprising supplying to the hydraulic system a hydraulic fluid composition having an ISO viscosity grade of 22 cSt or 32 cSt or 46 cSt or 68 cSt and comprising (a) at least 90 wt. % of a base oil having less than 500 ppm sulfur, (b) a calcium detergent in an amount sufficient to deliver 5 ppm to 200 ppm, or 5 ppm to 150 ppm, or 5 ppm to 100 ppm of calcium to the fluid and less than 10 mg of % or less than 5 ppm of zinc; and (e) 0.025 wt % to 0.75 wt % of an ashless surfactant comprising or consisting of an ashless polyisobutylene-based surfactant, such as a polyisobutylene-based succinimide derived from an aromatic polyamine.

[0098] The method of the present invention comprises operating the hydraulic system at a pressure equal to or higher than 300 bar. The method provided herein also comprises operating the pump at a speed equal to or higher than 2500 revolutions per minute.

[0099] The present invention also encompasses the use of a hydraulic fluid as described herein for lubricating and protecting hydraulic system components from wear.

[0100] In one embodiment, the invention includes the use of a hydraulic fluid for lubricating a hydraulic system, the hydraulic fluid having an ISO viscosity grade of 22 cSt or 32 cSt or 46 cSt or 68 cSt and comprising (a) at least 90% by weight of a base oil having less than 500 ppm sulfur, (b) a calcium detergent in an amount sufficient to deliver 5 ppm to 200 ppm, or 5 ppm to 150 ppm, or 5 ppm to 100 ppm calcium to the fluid and less than 10 mg of % or less than 5 ppm of zinc; and (e) 0.025 wt % to 0.75 wt % of an ashless surfactant comprising or consisting of an ashless polyisobutylene-based surfactant, such as a polyisobutylene-based succinimide derived from an aromatic polyamine.

[0101] In another embodiment, the present invention also includes the use of a hydraulic fluid for lubricating a hydraulic system, the hydraulic fluid having an ISO viscosity grade of 22 cSt or 32 cSt or 46 cSt or 68 cSt and comprising (a) at least 90 wt% of a base oil having less than 500 ppm sulfur, (b) a calcium detergent in an amount sufficient to deliver 5 ppm to 200 ppm, or 5 ppm to 150 ppm, or 5 ppm to 100 ppm calcium to the fluid and less than 10 mg of % or less than 5 ppm of zinc; and (e) 0.025 wt % to 0.75 wt % of an ashless surfactant comprising or consisting of an ashless polyisobutylene-based surfactant, such as a polyisobutylene-based succinimide derived from an aromatic polyamine.

[0102] A set of exemplary hydraulic lubricating compositions were prepared and evaluated as summarized in Table 1. Unless otherwise stated, all treatment grades were oil-free (ie, active). The example fluids were evaluated using the Micro Traction Machine (MTM Test) and the Bosch-Rexroth Pump Test as described below.

[0103]

[0104] 1. Nonylated naphthalenesulfonic acid, calcium salt, TBN 1.0, 50% diluent oil

[0105] 2. Methyl 3-((dialkoxythiophosphoryl)thio)propanoate with mixed C4 / C5 alkoxy groups

[0106] 3. 3-((Diisobutoxythiophosphoryl)thio)-2-methylpropanoic acid

[0107] 4. 4,4'-Methylenebis(dibutyl dithiocarbamate)

[0108] 5. Succinimide derived from aromatic polyamine (PIB Mn 2300 Da; TBN 0.1 mg KOH / g) (containing 50 wt% oil)

[0109] 6. Other additives include corrosion inhibitors, demulsifiers, defoaming additives, diluent oils and pour point depressants.

[0110] 7. The coefficient of friction of the embodiment composition was evaluated using a micro-traction machine (MTM) purchased from PCS Instruments. The test configuration is a bearing steel ball with a diameter of about 19.05 mm (3 / 4 inch) in contact with a highly polished surface on a bearing steel disc with a diameter of 46 mm. The ball is in contact with the disc so that rotation in the contact is eliminated. Rolling speed, sliding / rolling ratio, temperature and load are parameters that can be varied during each test. The sample speed is independently controlled using a servo motor to produce the desired sliding / rolling motion at the contact. The sample is contained in a sealed temperature-controlled reservoir containing about 35 ml of a fluid sample. The test temperature is controlled by an electric heater and the fluid temperature is monitored. The contact is automatically loaded to the desired Hertzian pressure, and the ball and disc speed are controlled by a motor. A series of tests for this study are run at a Hertzian pressure of about 1.00 GPa, a temperature of about 100°C, a rolling speed of about 100 mm / s and a fixed sliding and rolling ratio of about 100%. The test is carried out in stages of 10 minutes, with a total duration of about 120 minutes. After each 10 minute period, the rolling / sliding motion of the ball and disc in contact is stopped. The part of the ball in contact with the disc is pressed against a glass window. Using a microscope and a camera, images of the contact area on the ball are recorded. The test then continues with the next 10 minute segment. At the end of the test after 120 minutes, the recorded images are visually inspected and then analyzed to study the formation of the reaction film (tribographic film) and the changes in the thickness of the reaction film during each 10 minute test sequence. The formation of the film and the changes in the film thickness are then recorded over the duration of the 120 minute test time.

[0111] 8. "Rexroth Fluid Test Axial Piston Units Closed Loop Applications (RFT-APU-CL)", Bosch Program No. RE 96270, available upon request from the Bosch Rexroth website.

[0112] As used herein, "substantially free" means that the amount of the contemplated substance is below an amount that would affect the relevant properties of the fluid in a measurable manner. "Substantially free" may also mean that the contemplated substance is not intentionally added to the composition, but the presence of such materials as contaminants is not excluded. "Substantially free" may also mean that the contemplated substance may be present in an amount below the detection limit of a standard test method now known or later developed by one skilled in the art. In some embodiments, "substantially free" may mean less than 10 ppm by weight or even less than 5 ppm by weight.

[0113] It is known that some of the above-mentioned substances may interact in the final formulation so that the components of the final formulation may be different from those initially added. The products thus formed, including the products formed by using the lubricant composition of the present invention in its intended use, may not be susceptible to easy description. However, all such modifications and reaction products are included within the scope of the present invention. The present invention includes lubricating compositions prepared by mixing the above-mentioned components.

[0114] Each document mentioned above is incorporated herein by reference.Except in the examples or otherwise clearly indicated, all numerical values ​​of the specified material amount, reaction conditions, molecular weight, carbon number, etc. in this specification should be understood to be modified by the word "about".Unless otherwise stated, each chemical or composition mentioned herein should be interpreted as a commercial grade material, which may contain isomers, by-products, derivatives and other such materials generally understood to be present in the commercial grade.However, unless otherwise stated, the amount of each chemical component does not include any solvent or diluent oil, which may be present in commercial materials generally.It should be understood that the upper and lower limits of the amount, range and ratio described herein can be independently combined.Similarly, the scope and amount of each element of the present invention can be used together with the scope or amount of any other element.

[0115] Although the present invention has been explained with respect to its preferred embodiment, it should be understood that various modifications thereof will become apparent to those skilled in the art upon reading this specification. Therefore, it should be understood that the invention disclosed herein is intended to cover these modifications falling within the scope of the appended claims.

Claims

1. A hydraulic fluid comprising (a) at least 90 weight percent of a base oil having less than 500 ppm sulfur, (b) a calcium detergent in an amount that delivers 5 ppm to 200 ppm, or 5 ppm to 150 ppm, or 5 ppm to 100 ppm calcium to the fluid, and (c) at least one metal-free phosphorus-containing antiwear agent, and (d) one or more ashless antioxidants, wherein the hydraulic fluid has 10 ppm to 150 ppm phosphorus and wherein the hydraulic fluid is substantially free of zinc.

2. The hydraulic fluid of claim 1 wherein the calcium detergent comprises an alkylated aromatic sulfonate.

3. The hydraulic fluid of claim 2, wherein the calcium detergent comprises a neutral or overbased salt of an alkylated aromatic sulfonic acid.

4. The hydraulic fluid of claim 3, wherein the calcium detergent comprises or consists of a neutral salt of an alkylated aromatic sulfonic acid.

5. A hydraulic fluid according to any preceding claim, wherein the alkylated aromatic sulphonic acid comprises an alkyl group containing from 6 to 20 carbon atoms.

6. The hydraulic fluid of claim 5, wherein the alkyl group is branched.

7. The hydraulic fluid of claim 5, wherein the alkyl group is linear.

8. A hydraulic fluid according to any preceding claim, wherein the calcium detergent comprises or consists of a neutral salt of an alkylated naphthalene sulfonic acid.

9. The hydraulic fluid of any preceding claim, wherein the calcium detergent further comprises a calcium phenate detergent, a calcium salicylate detergent or a calcium salicylate detergent.

10. A hydraulic fluid according to any preceding claim, wherein the calcium detergent has a Total Base Number of less than 10 mg KOH / g according to ASTM D4739.

11. A hydraulic fluid according to any preceding claim, wherein the metal-free phosphorus-containing antiwear agent comprises or consists of a (thio)phosphate ester.

12. A hydraulic fluid according to any preceding claim, wherein the fluid comprises 0.02 to 3.0 wt%, or 0.03 to 1.5 wt%, or 0.05 to 0.5 wt% of the antioxidant.

13. A hydraulic fluid according to any preceding claim, further comprising an ashless surfactant.

14. The hydraulic fluid of claim 13, wherein the ashless surfactant comprises or consists of an ashless polyisobutylene-based surfactant.

15. The hydraulic fluid of claim 14, wherein the ashless polyisobutylene-based surfactant comprises or consists of a substituted polyisobutylene-based compound.

16. The hydraulic fluid of claim 15, wherein the substituted polyisobutylene compound comprises or consists of a polyisobutylene succinimide derived from an aromatic polyamine.

17. A hydraulic fluid according to any one of claims 13 to 16, wherein the fluid comprises 0.025 wt% to 0.75 wt% of the ashless surfactant.

18. A hydraulic fluid according to any preceding claim, wherein the fluid has an ISO viscosity grade of 22 cSt or 32 cSt or 46 cSt or 68 cSt.

19. A hydraulic fluid according to any preceding claim, wherein the fluid contains less than 10 ppm or even less than 5 ppm zinc.

20. A method of lubricating a hydraulic system, the method comprising supplying the hydraulic system with a hydraulic fluid composition as claimed in any one of claims 1 to 19.

21. The method of claim 20, wherein the hydraulic system operates at a pressure equal to or higher than 300 bar.

22. A method according to claim 20 or 21, wherein the hydraulic system comprises a pump operating at a speed equal to or higher than 2500 rpm.

23. Use of a composition as claimed in any one of claims 1 to 19 for lubricating a hydraulic system.

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