Durable Lubricating Fluids for Electric Vehicles

Abstract

To provide a durable lubricating fluid that maintains a low conductivity even after aging as a lubricating fluid for an electric motor or a hybrid-electric motor.SOLUTION: A durable lubricating composition comprises an oil of lubricating viscosity, a thiadiazole or derivative thereof, and an amine salt of phosphoric acid. The durable lubricating composition has a weight ratio ((S+P) / N) of sulfur plus phosphorus to nitrogen of at least 2.3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a durable lubricating fluid for electric or hybrid-electric motors. The disclosed technology relates to a durable lubricating fluid comprising an oil of lubricating viscosity, a thiadiazole or derivative thereof, and an amine salt of a phosphoric acid ester, and having a sulfur and phosphorus to nitrogen weight ratio ((S+P) / N) of at least 2.3. Such lubricants have a durable electrical conductivity of 50,000 pS / m. [Background technology]

[0002] A major challenge when developing lubricants for electric or hybrid-electric motors is developing lubricants that maintain relatively low electrical conductivity even after aging. These types of lubricants maintain relatively low electrical conductivity (or conversely, relatively high electrical resistivity) over the life of the lubricant to inhibit the buildup and discharge of static electricity within the electrified components found in electric or hybrid-electric motors.

[0003] Lubricating fluids for conventional internal combustion engines typically use additives to provide sufficient amounts of sulfur and phosphorus to provide wear and extreme pressure protection to mechanical components. However, such additives in lubricating fluids for electric or hybrid electric motors can pose problems because active sulfur and phosphorus compounds are often chemically aggressive to the copper wire and copper-based alloys used in electric and / or hybrid electric motors. In addition, sulfur and phosphorus compounds are often electrically conductive, and including active sulfur and phosphorus compounds in a lubricant can lead to an undesirable increase in the electrical conductivity of the lubricant. Therefore, lubricating fluids for electric and hybrid electric motors have the additional challenge of maintaining relatively low electrical conductivity while still protecting copper components and providing sufficient protection to mechanical components. Summary of the Invention

[0004] In one aspect or embodiment, a durable lubricating composition for electric or hybrid electric vehicles is described herein. In an embodiment, the lubricating composition includes a base oil of lubricating viscosity, at least about 0.7 weight percent of a thiadiazole or derivative thereof, and an amine salt of a phosphoric acid ester, providing the durable lubricating composition with at least about 100 ppm of phosphorus. The lubricating composition has a weight ratio of sulfur and phosphorus to nitrogen ((S+P) / N) of at least 2.3, and the lubricating composition has at least about 150 ppm of phosphorus and at least about 2000 ppm of sulfur, and a conductivity durability of about 50,000 pS / m or less. The conductivity durability is defined as the difference between the initial conductivity and the final conductivity, where the initial and final conductivity are measured at 1.5 volts, 20 Hz, and 160°C according to ATSM D2624-15, and the final conductivity is the difference between the initial conductivity and the final conductivity, where the lubricating composition has at least about 150 ppm of phosphorus and at least about 2000 ppm of sulfur. After aging at 170°C for 192 hours according to CEC L-48-A-00 To be measured.

[0005] In other aspects or embodiments, the thiadiazole of the durable lubricating composition may be selected from a mono-hydrocarbyl thiol-substituted thiadiazole, a bis-hydrocarbyl thiol-substituted thiadiazole, or a combination thereof, and / or the thiadiazole is a 1,3,4-thiadiazole or a derivative thereof, and / or the thiadiazole provides at least about 2000 ppm of sulfur to the durable lubricating composition, and / or the lubricating composition comprises greater than about 0.5 wt % to about 1 wt % of the thiadiazole or a derivative thereof, and / or the thiadiazole or a derivative thereof comprises one or more compounds having a structure of Formula I, [ka] wherein each R1 is independently hydrogen or sulfur, each R2 is independently an alkyl group, n is an integer of 0 or 1, and when R1 is hydrogen, the integer n of the adjacent R2 moiety is 0, and when R1 is sulfur, the integer n of the adjacent R2 moiety is 1, and at least one R1 is sulfur, and / or the thiadiazole or derivative thereof provides at least about 99% by weight of the sulfur to the durable lubricating composition.

[0006] In other aspects or embodiments, the durable lubricating compositions of any embodiment herein may include up to about 3500 ppm total sulfur and up to about 300 ppm total phosphorus.

[0007] In a further aspect or embodiment, the amine salt of a phosphoric acid ester of any embodiment herein comprises one or more monoalkyl phosphate esters and / or dialkyl phosphate esters, wherein the alkyl groups may be linear or branched, and / or the amine salt of a phosphoric acid ester is represented by Formula II: [ka] wherein R3 and R4 can independently be hydrogen or a linear, branched, or cyclic hydrocarbyl group; m is an integer from 0 to 1; p is an integer from 1 to 2; and m+p is equal to 2; R5, R6, R7, and R8 can independently be hydrogen or a hydrocarbyl group, and at least one of R5 to R8 is a hydrocarbyl group; and / or R3 and R4 can independently be a C3 to C10 alkyl group, and / or R3 and R4 are a C6 alkyl group; and / or R5, R6, At least one of R7 and R8 is a C10-C20 alkyl group, and / or two of R5, R6, R7, and R8 are independently a C10-C20 alkyl group, and / or two of R5, R6, R7, and R8 are independently a C12-C14 alkyl group, and / or the amine salt of a phosphate ester provides about 40 to about 90 weight percent of the total phosphorus in the durable lubricating composition, and / or the lubricating composition comprises about 0.25 to about 0.5 weight percent of the amine salt of a phosphate ester.

[0008] In other aspects or embodiments, the durable lubricating composition of any embodiment may have an initial conductivity of about 150,000 pS / m or less when measured at 160°C according to ASTM D2624-15 or less when measured at 160°C according to ASTM D2624-15.

[0009] In yet another aspect or embodiment, the present disclosure provides for the use of a durable lubricating composition (or method of lubrication) in an electric or hybrid-electric motor, the durable lubricating composition comprising a base oil of lubricating viscosity, at least about 0.7 weight percent thiadiazole or a derivative thereof, and an amine salt of a phosphoric acid ester providing the durable lubricating composition with at least about 100 ppm phosphorus, the durable lubricating composition having a weight ratio of sulfur and phosphorus to nitrogen ((S+P) / N) of at least 2.3, the lubricating composition having at least about 150 ppm phosphorus and at least about 2000 ppm sulfur, and an electrical conductivity durability of about 50,000 pS / m or less. The electrical conductivity durability is defined as the difference between the initial and final electrical conductivity, the initial and final electrical conductivity being measured at 1.5 volts, 20 Hz, and 160°C according to ASTM D2624-15, and the final electrical conductivity being determined by measuring the electrical conductivity of the lubricating composition. After aging at 170°C for 192 hours according to CEC L-48-A-00 The uses or methods herein may also include any of the features of any of the embodiments as described in this Summary of the Invention.

[0010] Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein.

[0011] To clarify the meaning of certain terms used herein, the following definitions are provided.

[0012] "Lubricating oil," "lubricant composition," "lubricating composition," "lubricant," and "lubricating and cooling fluid" refer to a finished lubricating product that includes a major amount of a base oil and a minor amount of an additive composition.

[0013] As used herein, the terms "additive package," "additive concentrate," "additive composition," and "transmission fluid additive package" refer to that portion of a lubricating oil composition excluding the major amount of base oil.

[0014] As used herein, the term "hydrocarbyl substituent" or "hydrocarbyl group" is used in its ordinary sense, as known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having a predominantly hydrocarbon character. Each hydrocarbyl group is independently selected from hydrocarbon substituents, where the substituted hydrocarbon substituents contain one or more of halo, hydroxyl, alkoxy, mercapto, nitro, nitroso, amino, pyridyl, furyl, imidazolyl, oxygen, and nitrogen, and no more than two non-hydrocarbon substituents are present for every 10 carbon atoms in the hydrocarbyl group.

[0015] As used herein, the term "weight percent" means the percentage that the recited component represents relative to the weight of the entire composition, unless expressly stated otherwise.

[0016] As used herein, the terms "soluble," "oil-soluble," or "dispersible" may, but do not necessarily, indicate that a compound or additive is soluble, dissolvable, miscible, or capable of being suspended in oil in any proportion. However, the terms mean that they are soluble, suspendable, dissolvable, or stably dispersible in oil to an extent sufficient to exert their intended effect in the environment in which the oil is extracted. Furthermore, if necessary, the incorporation of additional additives may allow for higher levels of loading of a particular additive.

[0017] As used herein, the term "alkyl" refers to straight, branched, cyclic, and / or substituted saturated chain moieties of about 1 to about 200 carbon atoms.

[0018] The term "alkenyl," as used herein, refers to straight, branched, cyclic, and / or substituted unsaturated chain moieties of about 3 to about 30 carbon atoms.

[0019] The term "aryl" as used herein refers to monocyclic and polycyclic aromatic compounds that may contain alkyl, alkenyl, alkylaryl, amino, hydroxyl, alkoxy, halo substituents, and / or heteroatoms including, but not limited to, nitrogen and oxygen.

[0020] As used herein, "number average molecular weight" or "Mn" is determined by gel permeation chromatography (GPC) using commercially available polystyrene standards (with Mn of 180 to about 18,000 as calibration standards). Additionally, the GPC method provides molecular weight distribution information; see, for example, W.W. Yau, J.J. Kirkland and D.D. Bly, "Modern Size Exclusion Liquid Chromatography," John Wiley and Sons, New York, 1979, which is also incorporated herein by reference.

[0021] Throughout this disclosure, terms such as "comprises," "includes," "contains," and the like are considered open-ended and include any element, step, or ingredient not expressly recited. The phrase "consists essentially of" means including any element, step, or ingredient that is expressly recited, as well as any additional elements, steps, or ingredients that do not materially affect the basic and novel aspects of the invention. The present disclosure also contemplates that any composition described using the terms "comprises," "includes," or "contains" should also be interpreted as including a disclosure of the same composition "consisting essentially of" or "consisting of" the specifically recited ingredients. [Brief explanation of the drawings]

[0022] [Figure 1]1 is a chart of conductivity durability versus sulfur, phosphorus, and nitrogen levels. DETAILED DESCRIPTION OF THE INVENTION

[0023] Disclosed herein are durable lubricating fluids suitable for use in electric or hybrid electric vehicles that contain sulfur and phosphorus to provide wear protection, but in a manner that unexpectedly maintains such relatively low electrical conductivity as the lubricant ages.

[0024] In one aspect or embodiment, the durable lubricating fluid herein comprises a base oil of lubricating viscosity, at least about 0.7 weight percent of a thiadiazole or derivative thereof, which provides sulfur and nitrogen to the fluid, and an amine salt of a phosphate ester, which provides phosphorus and nitrogen to the fluid. The fluid also has a weight ratio of sulfur and phosphorus to nitrogen ((S+P) / N) of at least 2.3, and has at least about 150 ppm phosphorus and at least about 2000 ppm sulfur. When the fluid comprises at least these additives and the provided ratios between sulfur, phosphorus, and nitrogen, the fluid exhibits a conductivity durability (described in more detail herein) of about 50,000 pS / m or less. In other aspects or embodiments, the fluid herein may also contain other phosphorus, nitrogen, and / or sulfur sources, so long as the fluid comprises the above-described thiadiazole or derivative thereof, the amine salt phosphate additive, and the above-specified ratios of sulfur, phosphorus, and nitrogen.

[0025] In other approaches, the phosphorus content of the fluid can be up to 300 ppm, up to 290 ppm, up to 270 ppm, up to 260 ppm, up to 250 ppm, up to 240 ppm, up to 230 ppm, up to 220 ppm, up to 200 ppm, up to 190, or up to 180. The fluid can also contain at least 150 ppm total phosphorus, or 150 ppm to 300 ppm phosphorus, or 180 to 300 ppm phosphorus, or any range therebetween, with at least a portion of the phosphorus being provided by the amine phosphate salt additive as described herein.

[0026] In other approaches, the sulfur content of the fluid may be up to 5000 ppm, up to 4500 ppm, up to 4000 ppm, up to 3500 ppm, up to 3000 ppm, or up to 2600 ppm. The fluid may also contain at least about 2000 ppm sulfur, or an amount of sulfur between about 2000 ppm and 5000 ppm, or any range therebetween. In some approaches, at least a portion of the sulfur, and most of the sulfur, is provided by a thiadiazole or derivative thereof as described herein. In some approaches, a thiadiazole or derivative thereof as described herein may provide at least about 98 percent of the total sulfur in the fluid.

[0027] As discussed further below, embodiments of fluids herein having a base oil, at least a thiadiazole or derivative thereof, and an amine salt of a phosphate ester additive generally have a kinematic viscosity of 4.5 cSt to 6.0 cSt at 100°C, exhibit an initial conductivity of about 150,000 pS / m or less as measured in accordance with ASTM D2624-15 (using an Epsilon+ electrical conductivity meter from Flucon Fluid Control GmbH or equivalent at 1.5 volts, 20 Hz, and 160°C), and exhibit a conductivity durability (absolute value, discussed in more detail below) of less than about 50,000 pS / m after aging the fluid at 170°C for 192 hours in accordance with CEC L-48-A-00. For fluids for electric or hybrid-electric motors, fluids with relatively low conductivity (i.e., higher resistivity) and minimal change in conductivity with aging (i.e., durability) are desired.

[0028] Base oil: Base oils or base oils of lubricating viscosity suitable for use in formulating durable lubricating fluids for use in electric and hybrid-electric motor vehicles according to the present disclosure may be selected from any suitable synthetic or natural oil or mixture thereof having a suitable lubricating viscosity. Natural oils may include animal oils, and vegetable oils (e.g., castor oil, lard oil), as well as liquid petroleum oils and mineral oils such as paraffinic, naphthenic, or mixed paraffin-naphthenic solvent-treated or acid-treated mineral lubricating oils.

[0029] Oils derived from coal or shale may also be suitable. Additionally, oils obtained from the Fischer-Tropsch gas-to-liquid process are also suitable. Fischer-Tropsch synthetic hydrocarbons are made from synthesis gas containing H2 and CO using a Fischer-Tropsch catalyst. Such hydrocarbons typically require further processing to be useful as base oils. These types of oils are commonly referred to as gas-to-liquids (GTL). Base oils may have a kinematic viscosity of 2 to 15 cSt at 100°C, as measured by ASTM D2270-10(2016).

[0030] The base oil used in the fluids described herein may be a single base oil or a mixture of two or more base oils. Specifically, the one or more base oils may desirably be selected from any of Groups II through V of the base oils designated in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. Such base oil groups are set forth in Table 1 as follows:

[0031] [Table 1]

[0032] In one variation, in any of the embodiments herein, the base oil may be selected from Group II through Group V base oils, or mixtures of these base oils. In one embodiment, the base oil comprises a Group III base oil, or a blend of a Group III base oil with a Group II, Group IV, and / or Group V base oil.

[0033] API Group III base oils can include oils derived from Fischer-Tropsch synthesized hydrocarbons. Fischer-Tropsch synthesized hydrocarbons are made from synthesis gas containing H2 and CO using a Fischer-Tropsch catalyst. Such hydrocarbons typically require further processing to be useful as base oils. These types of oils are commonly referred to as gas-to-liquids (GTL). For example, the hydrocarbons can be hydroisomerized using the processes disclosed in U.S. Patent Nos. 6,103,099 or 6,180,575, hydrocracked and hydroisomerized using the processes disclosed in U.S. Patent Nos. 4,943,672 or 6,096,940, dewaxed using the process disclosed in U.S. Patent No. 5,882,505, or hydroisomerized and dewaxed using the processes disclosed in U.S. Patent Nos. 6,013,171, 6,080,301, or 6,165,949.

[0034] PAOs, which are API Group IV base oils, are typically derived from monomers having 4 to 30, or 4 to 20, or 6 to 16 carbon atoms. Examples of PAOs that can be used in the present invention include those derived from octene, decene, mixtures thereof, and the like. The PAOs can have a kinematic viscosity at 100°C of 2 to 15, or 3 to 12, or 4 to 8 cSt, as measured by ASTM D2270-10. Examples of PAOs include a 4 cSt PAO at 100°C, a 6 cSt PAO at 100°C, and mixtures thereof.

[0035] Group V base oils include synthetic and natural ester base fluids. Synthetic esters may include esters of dicarboxylic acids and monohydric alcohols. Specific examples of these esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, diicosyl sebacate, and the 2-ethylhexyl diester of linoleic acid dimer. Other group V esters include C5-C6 12 Also included are those formed from monocarboxylic acids and polyols and polyol ethers, such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, etc. Esters are also monoesters of monocarboxylic acids and monohydric alcohols.

[0036] Natural esters refer to materials derived from renewable biological resources, organisms, or entities, as opposed to materials derived from petroleum or equivalent raw materials. Natural esters include fatty acid triglycerides, hydrolyzed or partially hydrolyzed triglycerides, or transesterified triglyceride esters such as fatty acid methyl esters (FAMEs). Suitable triglycerides include, but are not limited to, palm oil, soybean oil, sunflower oil, rapeseed oil, olive oil, linseed oil, and related materials.

[0037] The base oil may be combined with selected sulfur and phosphorus-providing additives, as well as other optional additives, as disclosed in embodiments herein to provide a lubricating fluid for use in electric motor vehicles. Thus, the base oil may be present in the lubricating fluid in an amount greater than about 80 wt. %, or greater than about 90 wt. %, based on the total weight of the lubricating fluid. In some embodiments, the base oil may be present in the lubricating fluid in an amount greater than about 95 wt. %, based on the total weight of the lubricating fluid.

[0038] Thiadiazole Additives: The durable lubricating compositions herein include a thiadiazole or derivative thereof in an amount of about 0.7 wt. % or greater. In some approaches, about 0.7 wt. % to about 1 wt. %, or about 0.7 wt. % to about 0.9 wt. % of the thiadiazole or derivative thereof is present in the durable lubricating composition. In some embodiments, the thiadiazole or derivative thereof is a mixture of thiadiazole compounds and / or hydrocarbyl-substituted derivatives thereof.

[0039] In some approaches, the thiadiazole or derivative thereof provides the durable lubricating composition with at least about 2000 ppm sulfur, in other approaches at least about 2200 ppm sulfur, at least about 2400 ppm sulfur, at least about 2600 ppm sulfur, at least about 2800 ppm sulfur, or at least about 2900 ppm sulfur. In other approaches, the thiadiazole or derivative thereof may also provide the durable lubricating composition with up to about 3500 ppm sulfur, and in other approaches up to about 3150 ppm sulfur.

[0040] Surprisingly, the form and amount of thiadiazole or derivative thereof contributes to the electrical conductivity durability of the lubricating composition while providing sulfur to provide wear performance characteristics. In this manner, the thiadiazole or derivative thereof comprises one or more compounds having the structure of Formula I: [ka] wherein each R1 is independently hydrogen or sulfur, each R2 is independently an alkyl group, and n is an integer of 0 or 1, and when R1 is hydrogen, the integer n of adjacent R2 moieties is 0, and when R1 is sulfur, the integer n of adjacent R2 moieties is 1, with the proviso that at least one R1 is sulfur. In another approach, the thiadiazole additive is a blend of compounds of formula Ia and formula Ib, as shown below: [ka] In formula Ia, each integer n is 1, each R1 is sulfur, and each R2 is a C5 to C15 alkyl group, preferably a C8 to C12 alkyl group; [ka] In Formula Ib, one integer n is 1, the associated R2 group is a C5-C15 alkyl group (preferably a C8-C12 alkyl group), the associated R1 group is sulfur, and the other integer n is 0, the associated R1 group is hydrogen. In some embodiments, the thiadiazole or derivative thereof comprises a blend of Formulas Ia and Ib, where Formula Ia is the majority of the blend, and in other approaches, the blend of Ia and Ib is about 75 to about 90 weight percent Ia and about 10 to about 25 weight percent Ib (or other ranges therein). In another approach, the thiadiazole is a 2,5-dimercapto-1,3,4-thiadiazole, including a blend of 2,5-bis-(nonyldithio)-1,3,4-thiadiazole (e.g., about 75 to about 90%) and 2,5-mono-(nonyldithio)-1,3,4-thiadiazole (e.g., about 10 to about 25%). In other approaches or embodiments, examples of thiadiazole compounds that may be used in the fluids herein include 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazole, 2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazole, 2,5-bis(hydrocarbylthio)-1,3,4-thiadiazole, 2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazole, variations thereof, or combinations thereof. 1,3,4-Thiadiazoles are generally synthesized from hydrazine and carbon disulfide by known methods. See, for example, U.S. Patent Nos. 2,765,289, 2,749,311, 2,760,933, 2,850,453, 2,910,439, 3,663,561, 3,862,798, and 3,840,549.

[0041] In yet other approaches, the thiadiazole or derivative thereof may also provide a majority of the sulfur in the durable lubricating compositions herein. In some approaches, the selected thiadiazole or derivative herein may provide at least about 98 wt. % of the total sulfur in the lubricating composition, or at least about 99 wt. % of the total sulfur. As discussed further below, the compositions herein also have a selected relationship of sulfur and phosphorus to nitrogen to achieve robust electrical conductivity durability performance.

[0042] In some approaches or embodiments, the fluids herein comprise at least about 0.7 weight percent, at least about 0.8 weight percent, or at least about 0.85 weight percent thiadiazole or a derivative thereof, and in some embodiments less than about 1 weight percent, less than about 0.95 weight percent, or less than about 0.9 weight percent thiadiazole or a derivative thereof.

[0043] Phosphorus Additive: The durable lubricating compositions herein also include a phosphorus additive in an amount of about 0.25 wt. % to about 0.5 wt. %. In some approaches or embodiments, the selected phosphorus additive is an amine salt of a phosphorus ester in an amount to provide the durable lubricating composition with at least about 100 ppm phosphorus (in other approaches, from about 130 ppm phosphorus to about 160 ppm phosphorus in the lubricating compositions herein). The amine salt of a phosphorus ester can include one or more monoalkyl phosphate esters, dialkyl phosphate esters, and / or mixtures thereof, where the alkyl groups can be linear, branched, or cyclic. The fluids herein can also include other compounds that provide phosphorus, but in some embodiments, the amine salt of a phosphorus ester herein provides about 40 to about 90 wt. % of the total phosphorus in the durable lubricating composition (in other embodiments, from about 50 to about 80 wt. % of the phosphorus, or from about 50 to about 70 wt. % of the phosphorus in the lubricating compositions herein).

[0044] In an approach or embodiment, the amine salt of a phosphoric acid ester may be represented by Formula II: [ka] wherein R3 and R4 can independently be hydrogen or a linear, branched, or cyclic hydrocarbyl group, m is an integer from 0 to 1, p is an integer from 1 to 2, and m+p is equal to 2, and R5, R6, R7, and R8 can independently be hydrogen or a hydrocarbyl group, and at least one of R5-R8 is a hydrocarbyl group. Examples of suitable alkyl or hydrocarbyl groups for R3 and / or R4 include linear or branched alkyl groups such as, but not limited to, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and / or decyl groups. In yet another exemplary approach, R3 and R4 can be cyclic hydrocarbyl groups, examples of which include cyclopentyl, cyclohexyl, cycloheptyl, methylcyclopentyl, dimethylcyclopentyl, methylcyclopentyl, dimethylcyclopentyl, methylethylcyclopentyl, diethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, methylethylcyclohexyl, diethylcyclohexyl, methylcycloheptyl, dimethylcycloheptyl, methylethyl-cycloheptyl, and / or diethylcycloheptyl. In some approaches or embodiments, suitable amine salts of phosphate esters are mixtures of monoalkyl and dialkyl phosphate esters. The monoalkyl and dialkyl groups can be linear, branched, or cyclic, as described above.

[0045] Amine salts of phosphoric acid esters are known to those skilled in the art and can be derived from primary, secondary, or tertiary amines, or mixtures thereof. Exemplary amines suitable for the salts can be aliphatic, cyclic, aromatic, or non-aromatic, but are generally aliphatic amines. Examples of suitable primary amines include ethylamine, propylamine, butylamine, 2-ethylhexylamine, bis-(2-ethylhexyl)amine, octylamine, and dodecylamine, as well as fatty amines such as n-octylamine, n-decylamine, n-dodecylamine, n-tetradecylamine, n-hexadecylamine, n-octadecylamine, or oleylamine. Examples of suitable secondary amines include dimethylamine, diethylamine, dipropylamine, dibutylamine, diamylamine, dihexylamine, diheptylamine, methylethylamine, ethylbutylamine, N-methyl-1-amino-cyclohexane, and / or ethylamylamine. The secondary amine may also be a cyclic amine such as piperidine, piperazine, and morpholine. Examples of suitable tertiary amines include tri-n-butylamine, tri-n-octylamine, tri-decylamine, tri-laurylamine, tri-hexadecylamine, and / or dimethyl-oleylamine.

[0046] In some approaches, the amine of Formula II above can have at least one of the R5, R6, R7, or R8 groups that is a C10-C20 alkyl group, and in other approaches or embodiments, at least two of the R5, R6, R7, or R8 groups are independently a C10-C20 alkyl group. In some embodiments, at least two of the R5, R6, R7, or R8 groups are independently a C12-C14 alkyl group.

[0047] The amine salt of a phosphoric acid ester may be as described in U.S. Pat. No. 9,574,156, which is incorporated herein by reference, and may be prepared by reacting a suitable phosphorus compound with an amine to form the amine salt of a phosphoric acid ester. In one embodiment, the amine salt of a phosphoric acid ester may be of formula (II), where R3 and R4 can independently be C6 or hydrogen, m is an integer from 0 to 1, p is an integer from 1 to 2, and m + p is equal to 2. R5, R6, R7, and R8 can independently be hydrogen or a C12 to C14 hydrocarbyl group, and at least one of R5 to R8 is a C12 to C14 hydrocarbyl group. In this manner, the amine salt of a phosphoric acid ester may be present in the durable lubricating fluids herein in an amount of at least about 0.25 weight percent, or at least about 0.3 weight percent, or up to about 0.5 weight percent, or up to about 0.35 weight percent of the lubricating composition.

[0048] Lubricating oil composition: The durable lubricating composition herein comprises, in majority, a base oil of lubricating viscosity, a thiadiazole or derivative thereof, which provides sulfur and nitrogen to the fluid, and an amine salt of a phosphate ester, which provides phosphorus and nitrogen to the fluid. The lubricating composition may optionally contain other additives. While sulfur and phosphorus can be problematic in fluids for electric or hybrid electric motors in maintaining relatively low electrical conductivity, it has been surprisingly found that when the phosphorus and sulfur are provided by at least these additives and the fluid also contains levels of phosphorus, sulfur, and nitrogen provided in a selected sulfur and phosphorus to nitrogen weight ratio ((S+P) / N) of at least about 2.3, the fluid exhibits a small change in electrical conductivity after aging. For example, the fluid has a relatively low initial electrical conductivity when measured at 1.5 volts, 20 Hz, and 160°C according to ASTM D2624-15. The electrical conductivity of the fluid is measured again according to the same procedure, but after the fluid has been aged. The aging process is in accordance with CEC L-48-A-00 at 170°C for 192 hours. The change in conductivity between the initial conductivity measurement and the conductivity measurement after aging is about 50,000 pS / m or less. Thus, these fluids maintain relatively low electrical conductivity characteristics after aging and are considered durable lubricating compositions. In other embodiments, the selected weight ratio to achieve fluid durability is at least about 2.4, at least about 2.7, or at least about 2.9, preferably less than 4.0, less than 3.5, less than 3.3, less than 3.1, or less than 3.0.

[0049] In embodiments, the fluids herein may also exhibit an initial conductivity of about 140,000 pS / m or less, or about 70,000 pS / m or less, and in some approaches about 50,000 pS / m or more, or about 60,000 pS / m or more. In other embodiments, the fluids also exhibit an electrical conductivity durability (measured as the difference between the initial conductivity and the conductivity after aging) of about 50,000 pS / m or less, about 40,000 pS / m or less, about 30,000 pS / m or less, or about 20,000 pS / m or less, about 10,000 pS / m or less, about 5,000 pS / m or less, or even about 2,000 pS / m or less.

[0050] Other Additives: The lubricating fluids described herein may also include one or more additional additives. For example, the fluid may include at least one component selected from the group including antioxidants, friction modifiers, detergents, corrosion inhibitors, copper corrosion inhibitors, antifoam agents, seal swell agents, extreme pressure agents, antiwear agents, viscosity modifiers, dispersants, and combinations thereof. The other performance additives, in addition to those identified above, may also include one or more of metal deactivators, demulsifiers, pour point depressants, and mixtures thereof.

[0051] Antioxidants: In some embodiments, the lubricating fluid contains one or more antioxidants. Suitable antioxidants include phenolic antioxidants, aromatic amine antioxidants, sulfurized phenolic antioxidants, and organic phosphites, among others.

[0052] Examples of phenolic antioxidants include 2,6-di-tert-butylphenol, liquid mixtures of tertiary butylated phenols, 2,6-di-tert-butyl-4-methylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), mixed methylene-bridged polyalkylphenols, and 4,4'-thiobis(2-methyl-6-tert-butylphenol). N,N'-di-sec-butyl-phenylenediamine, 4-isopropylaminodiphenylamine, phenyl-alpha-naphthylamine, phenyl-alpha-naphthylamine, and ring-alkylated diphenylamines. Examples include sterically hindered tertiary butylated phenols, bisphenols, and cinnamic acid derivatives, as well as combinations thereof.

[0053] Aromatic amine antioxidants include, but are not limited to, diarylamines having the formula: [ka] In the formula, R' and R" each independently represent a substituted or unsubstituted aryl group having 6 to 30 carbon atoms. Examples of the substituent on the aryl group include an alkyl group having 1 to 30 carbon atoms, a hydroxy group, a halogen group, a carboxylic acid or ester group, or an aliphatic hydrocarbon group such as a nitro group.

[0054] The aryl group is preferably substituted or unsubstituted phenyl or naphthyl, especially one in which one or both aryl groups are substituted with at least one alkyl having from 4 to 30, preferably from 4 to 18, and most preferably from 4 to 9 carbon atoms. It is preferred that one or both aryl groups are substituted, e.g., mono-alkylated diphenylamine, di-alkylated diphenylamine, or a mixture of mono- and di-alkylated diphenylamines.

[0055] Examples of diarylamines that can be used include, but are not limited to, diphenylamine, various alkylated diphenylamines, 3-hydroxydiphenylamine, N-phenyl-1,2-phenylenediamine, N-phenyl-1,4-phenylenediamine, monobutyldiphenylamine, dibutyldiphenylamine, monooctyldiphenylamine, dioctyldiphenylamine, monononyldiphenylamine, dinonyldiphenylamine, monotetradecyldiphenylamine, ditetradecyldiphenylamine, phenyl-alpha-naphthylamine, monooctylphenyl-alphanaphthylamine, phenyl-beta-naphthylamine, monoheptyldiphenylamine, diheptyldiphenylamine, p-oriented styrenated diphenylamines, mixed butyloctyldiphenylamines, and mixed octylstyryldiphenylamines.

[0056] Sulfur-containing antioxidants include, but are not limited to, sulfurized olefins, characterized by the type of olefin used in their production and the final sulfur content of the antioxidant. High molecular weight olefins, i.e., olefins having an average molecular weight of 168 to 351 g / mol, are preferred. Examples of usable olefins include alpha-olefins, isomerized alpha-olefins, branched olefins, cyclic olefins, and combinations thereof.

[0057] Alpha olefins include, but are not limited to, any C4 to C25 alpha olefin. Alpha olefins may be isomerized prior to or during the sulfurization reaction. Structural and / or conformational isomers of alpha olefins containing internal double bonds and / or branching may also be used. For example, isobutylene is the branched olefin counterpart of the alpha-olefin 1-butene.

[0058] Sulfur sources that can be used in the sulfurization reaction of olefins include elemental sulfur, sulfur monochloride, sulfur dichloride, sodium sulfide, sodium polysulfide, and mixtures thereof added together at different stages of the sulfurization process.

[0059] Unsaturated oils, due to their unsaturation, may be sulfurized and used as antioxidants. Examples of fats and oils that can be used include corn oil, canola oil, cottonseed oil, grapeseed oil, olive oil, palm oil, peanut oil, coconut oil, rapeseed oil, safflower seed oil, sesame oil, soybean oil, sunflower seed oil, tallow, and combinations thereof.

[0060] The total amount of antioxidant in the lubricating fluids described herein may be present in an amount to deliver up to 200 ppm nitrogen, or up to 175 ppm nitrogen, or 150-200 ppm nitrogen.

[0061] Friction Modifiers: Suitable additional friction modifiers include metal-containing and metal-free friction modifiers and may include imidazolines, aliphatic fatty acid amides, aliphatic amines, succinimides, alkoxylated fatty amines, ether amines, alkoxylated ether amines, amine oxides, amidoamines, nitriles, betaines, quaternary amines, imines, amine salts, aminoguanidines, alkanolamides, phosphonates, metal-containing compounds, glycerin esters, sulfurized fatty compounds and olefins, naturally occurring animal and vegetable oils such as sunflower oil, dicarboxylic acid esters, esters or partial esters of polyols with one or more aliphatic or aromatic carboxylic acids, and the like.

[0062] Suitable friction modifiers may contain hydrocarbyl groups selected from linear, branched, or aromatic hydrocarbyl groups, or mixtures thereof, and such hydrocarbyl groups may be saturated or unsaturated. The hydrocarbyl groups may be composed of carbon and hydrogen or heteroatoms such as sulfur or oxygen. The hydrocarbyl groups may range from 12 to 25 carbon atoms. In some embodiments, the friction modifier may be a long-chain fatty acid ester. In other embodiments, the long-chain fatty acid ester may be a monoester, diester, or (tri)glyceride. The friction modifier may be a long-chain fatty amide, long-chain fatty ester, long-chain fatty epoxide derivative, or long-chain imidazoline.

[0063] Other suitable friction modifiers may include organic, ashless (metal-free), nitrogen-free organic friction modifiers. Such friction modifiers may include esters formed by reacting carboxylic acids and anhydrides with alkanols, and generally contain a polar end group (e.g., carboxyl or hydroxyl) covalently bonded to an oleophilic hydrocarbon chain. An example of an organic ashless, nitrogen-free friction modifier is commonly known as glycerol monooleate (GMO), which may include mono-, di-, and tri-esters of oleic acid. Other suitable friction modifiers are described in U.S. Patent No. 6,723,685.

[0064] Amine-based friction modifiers may include amines or polyamines. Such compounds may have hydrocarbyl groups that are either saturated or unsaturated, linear, or a mixture thereof, and may contain 12 to 25 carbon atoms. Further examples of suitable friction modifiers include alkoxylated amines and alkoxylated ether amines. Such compounds may have hydrocarbyl groups that are either saturated, unsaturated, or a mixture thereof, linear. They may contain from about 12 to about 25 carbon atoms. Examples include ethoxylated amines and ethoxylated ether amines.

[0065] The amines and amides can be used as such or in the form of adducts or reaction products with boron compounds such as boron oxide, boron halides, metaborates, boric acid or mono-, di-, or tri-alkyl borates. Other suitable friction modifiers are described in U.S. Pat. No. 6,300,291.

[0066] When the additional friction modifier contains nitrogen, such additional friction modifier may be present in the lubricating fluid in an amount to deliver up to 200 ppm nitrogen, or up to 150 ppm nitrogen, or 100 to 150 ppm nitrogen.

[0067] Detergent: The metal detergents contained in the lubricating fluids described herein generally comprise a polar head and a long hydrophobic tail, with the polar head consisting of a metal salt of an acidic organic compound. The salts may contain substantially stoichiometric amounts of metal, in which case they are usually described as normal or neutral salts, and typically have a total base number, or TBN (as measured by ASTM D2896), of from about 0 to less than about 150. Large amounts of metal base can be obtained by reacting an excess of a metal compound, such as an oxide or hydroxide, with an acidic gas, such as carbon dioxide. The resulting overbased detergent comprises micelles of neutralized detergent surrounding a core of inorganic metal base (e.g., hydrated carbonate). Such overbased detergents may have a TBN of about 150 or greater, e.g., from about 150 to about 450 or greater.

[0068] Detergents that may be suitable for use in this embodiment include oil-soluble overbased, underbased, and neutral sulfonates, phenates, sulfurized phenates, and salicylates, especially of alkali or alkaline earth metals, such as sodium, potassium, lithium, calcium, and magnesium. More than one metal may be present, for example, both calcium and magnesium. Mixtures of calcium and / or magnesium with sodium may also be suitable. Suitable metal detergents may be overbased calcium or magnesium sulfonates having a TBN of 150 to 450 TBN, overbased calcium or magnesium phenates or sulfurized phenates having a TBN of 150 to 300 TBN, and overbased calcium or magnesium salicylates having a TBN of 130 to 350 TBN. Mixtures of such salts may also be used.

[0069] The metal-containing detergent may be present in the lubricating fluid in an amount sufficient to improve the corrosion inhibitor performance of the fluid. The metal-containing detergent may be present in the fluid in an amount sufficient to provide up to 200 ppm of alkali and / or alkaline earth metals, based on the total weight of the lubricating fluid. In one example, the metal-containing detergent may be present in an amount sufficient to provide 100 to 200 ppm of alkali and / or alkaline earth metals. In another embodiment, the metal-containing detergent may be present in an amount sufficient to provide 100 to 150 ppm of alkali and / or alkaline earth metals.

[0070] Corrosion Inhibitors: Rust inhibitors or corrosion inhibitors may also be included in the lubricating compositions described herein. Such materials include monocarboxylic and polycarboxylic acids. Examples of suitable monocarboxylic acids are octanoic acid, decanoic acid, and dodecanoic acid. Suitable polycarboxylic acids include dimer and trimer acids made from acids such as tall oil fatty acids, oleic acid, and linoleic acid. Suitable copper corrosion inhibitors include ether amines, polyethoxylated compounds such as ethoxylated amines and ethoxylated alcohols, imidazolines, monoalkyl and dialkyl thiadiazoles, and the like. Additional compounds include monocarboxylic and polycarboxylic acids. Examples of suitable monocarboxylic acids are octanoic acid, decanoic acid, and dodecanoic acid. Suitable polycarboxylic acids include dimer and trimer acids made from acids such as tall oil fatty acids, oleic acid, and linoleic acid.

[0071] Thiazoles and triazoles may also be used in lubricants. Examples include benzotriazole, tolyltriazole, octyltriazole, decyltriazole, dodecyltriazole, and 2-mercaptobenzotriazole.

[0072] Another useful class of rust inhibitors are alkenyl succinic acid and alkenyl succinic anhydride corrosion inhibitors, such as tetrapropenyl succinic acid, tetrapropenyl succinic acid, tetrapropenyl succinic anhydride, tetradecenyl succinic acid, tetradecenyl succinic anhydride, hexadecenyl succinic acid, and hexadecenyl succinic anhydride. Half esters of alkenyl succinic acids having 8 to 24 carbon atoms in the alkenyl group with alcohols such as polyglycols are also useful. Other suitable rust or corrosion inhibitors include ether amines, acidic phosphoric acids, amines, polyethoxylated compounds such as ethoxylated amines, ethoxylated phenols, and ethoxylated alcohols, imidazolines, aminosuccinic acids or their derivatives, and the like.

[0073] Mixtures of such rust inhibitors or corrosion inhibitors may be used. The total amount of corrosion inhibitor, if present in the lubricating compositions described herein, may be up to 1.0 wt. %, or may range from 0.01 to 0.5 wt. %, based on the total weight of the lubricating composition.

[0074] Extreme Pressure Agents: The lubricating fluids described herein may optionally contain one or more extreme pressure (EP) agents. Oil-soluble EP agents include sulfur and chlorosulfur-containing EP agents, chlorinated hydrocarbon EP agents, and phosphorus EP agents. Examples of such EP agents include chlorinated waxes; organic sulfides and polysulfides such as dibenzyl disulfide, bis(chlorobenzyl) disulfide, dibutyl trisulfide, sulfurized methyl ester of oleic acid, sulfurized alkylphenols, dipentene sulfide, sulfurized terpenes, and sulfurized Diels-Alder adducts; phosphorus sulfurized hydrocarbons such as the reaction products of phosphorus sulfide with turpentine or methyl oleate; phosphorus esters such as dihydrocarbyl and trihydrocarbyl phosphites, e.g., dibutyl phosphite, diheptyl phosphite, dicyclohexyl phosphite, and pentylphenyl phosphite; dipentylphenyl phosphite, tridecyl phosphite, distearyl phosphite, and polypropylene-substituted phenyl phosphites; metal thiocarbamates such as zinc dioctyldithiocarbamate and barium heptylphenol diacid; amine salts of alkyl and dialkyl phosphates, including, for example, the amine salt of the reaction product of a dialkyldithiophosphoric acid with propylene oxide; and mixtures thereof.

[0075] Antiwear Agents: The lubricating oil compositions herein may also optionally contain one or more additional antiwear agents. Examples of suitable antiwear agents include, but are not limited to, phosphate esters or salts thereof; phosphoric acid esters; phosphites; phosphonates, phosphorus-containing carboxylic acid esters, ethers, or amides; oil-soluble amine salts of phosphorus compounds; sulfurized olefins; thiocarbamate-containing compounds, including thiocarbamate esters, alkylene-linked thiocarbamates, and bis(S-alkyldithiocarbamyl)disulfides; and mixtures thereof.

[0076] The antiwear agent may be present in a range including from about 0 wt % to about 1 wt %, in another approach from about 0.01 wt % to about 0.8 wt %, in yet another approach from about 0.05 wt % to about 0.5 wt %, or in a further approach from about 0.1 wt % to about 0.3 wt % of the lubricating oil composition.

[0077] Viscosity Modifiers: The lubricating fluid may optionally contain one or more viscosity modifiers. Suitable viscosity index improvers may include polyolefins, olefin copolymers, ethylene / propylene copolymers, polyisobutene, hydrogenated styrene-isoprene polymers, styrene / maleic acid ester copolymers, hydrogenated styrene / butadiene copolymers, hydrogenated isoprene polymers, alpha-olefin maleic anhydride copolymers, polymethacrylates, polyacrylates, polyalkylstyrenes, hydrogenated alkenylaryl conjugated copolymers, or mixtures thereof. Viscosity index improvers may include star polymers, suitable examples of which are described in U.S. Publication No. 2012 / 0101017(A1).

[0078] The lubricating fluids described herein may also optionally include one or more dispersant viscosity modifiers in addition to or in place of a viscosity modifier. Suitable dispersant viscosity modifiers may include functionalized polyolefins, such as ethylene-propylene copolymers functionalized with the reaction product of an acylating agent (e.g., maleic anhydride) and an amine, amine-functionalized polymethacrylates, or esterified maleic anhydride-styrene copolymers reacted with amines.

[0079] The total amount of viscosity modifier and / or dispersant viscosity modifier, if present, may be up to 1.0 wt. %, or up to 0.5 wt. %, or up to 0.3 wt. %, based on the total weight of the lubricating fluid.

[0080] Dispersants: Lubricating fluids may contain one or more dispersants. The dispersant may be an ashless dispersant with a polar group attached to a relatively high molecular weight hydrocarbon chain. Examples of such dispersants are N-substituted long-chain alkenyl succinimides, succinate ester dispersants, succinate ester-amide dispersants, Mannich base dispersants, polymeric polyamine dispersants, their phosphated forms, and their boronated forms. The dispersant may be capped with an acidic molecule capable of reacting with secondary amino groups.

[0081] The N-substituted long chain alkenyl succinimides may contain polyisobutylene (PIB) substituents, where the number average molecular weight of the polyisobutylene substituent is in the range of about 500 to 5000. The PIB substituents used in the dispersants also have a viscosity at 100°C of about 2100 to about 2700 cSt, as determined using ASTM D445.

[0082] The polyisobutylene moiety in the dispersant preferably has a narrow molecular weight distribution (MWD), also called polydispersity, as determined by the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn). Polymers with Mw / Mn less than 2.2, preferably less than 2.0, are most desirable. Suitable polyisobutylene substituents have a polydispersity of about 1.5 to 2.1, or about 1.6 to about 1.8.

[0083] The dicarboxylic acid or anhydride can be selected from carboxylic reactants, including the corresponding acid halides and C1-C4 aliphatic esters, such as maleic anhydride, maleic acid, fumaric acid, malic acid, tartaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, mesaconic acid, ethyl maleic anhydride, dimethyl maleic anhydride, ethyl maleic acid, dimethyl maleic acid, and hexyl maleic acid. The molar ratio of dicarboxylic acid or anhydride to hydrocarbyl moieties in the reaction mixture used to prepare the hydrocarbyl dicarboxylic acid or anhydride can vary widely. Thus, the molar ratio can vary from 5:1 to 1:5, for example, from 3:1 to 1:3. A molar ratio of acid or anhydride to hydrocarbyl moieties of 1:1 to less than 1.6:1 is particularly preferred. Other useful molar ratios of dicarboxylic acid or anhydride to hydrocarbyl moieties are from 1.3:1 to 1.7:1, or from 1.3:1 to 1.6:1, or from 1.3:1 to 1.5:1.

[0084] Any of a number of polyalkylene polyamines can be used to prepare the dispersant additive. Non-limiting exemplary polyamines include aminoguanidine bicarbonate (AGBC), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), and heavy polyamines. Heavy polyamines may include mixtures of polyalkylene polyamines, primarily containing oligomers with seven or more nitrogen atoms per molecule, two or more primary amines, and more extensive branching than conventional polyamine mixtures, although they contain small amounts of polyamine oligomers such as TEPA and PEHA. Typically, these heavy polyamines have an average of 6.5 nitrogen atoms per molecule. Additional non-limiting polyamines that may be used to prepare hydrocarbyl-substituted succinimide dispersants are disclosed in U.S. Patent No. 6,548,458, the disclosure of which is incorporated herein by reference in its entirety. The molar ratio of hydrocarbyl dicarboxylic acid or anhydride to polyalkylene polyamine may be from about 1:1 to about 3.0:1.

[0085] Mannich base dispersants are typically reaction products of alkylphenols having long-chain alkyl substituents on the ring with one or more aliphatic aldehydes containing from about 1 to about 7 carbon atoms (especially formaldehyde and its derivatives), and may be polyamines (especially polyalkylene polyamines). For example, Mannich base ashless dispersants can be formed by condensing about 1 mole of a long-chain hydrocarbon-substituted phenol with about 1 to about 2.5 moles of formaldehyde and about 0.5 to about 2 moles of a polyalkylene polyamine.

[0086] The dispersants described herein may be borated and / or phosphated. These dispersants are generally the reaction product of i) at least one phosphorus and / or boron compound, and ii) at least one ashless dispersant.

[0087] Suitable boron compounds useful in forming the dispersants herein include any boron compound or mixture of boron compounds capable of introducing a boron-containing species into the ashless dispersant. Any organic or inorganic boron compound capable of undergoing such a reaction can be used. Thus, boron oxide, boron oxide hydrate, boron trifluoride, boron tribromide, boron trichloride, HBF4 boric acids such as boronic acids (e.g., alkyl-B(OH)2 or aryl-B(OH)2), boric acid (i.e., H3BO3), tetraboric acid (i.e., H2BO7), metaboric acid (i.e., HBO2), ammonium salts of such boric acids, and esters of such boric acids can be used. The use of complexes of boron trihalides with ethers, organic acids, inorganic acids, or hydrocarbons is a convenient means of introducing the boron reactant into the reaction mixture. Such complexes are known and are exemplified by boron trifluoride-diethyl ether, boron trifluoride-phenol, boron trifluoride-phosphoric acid, boron trichloride-chloroacetic acid, boron tribromide-dioxane, and boron trifluoride-methyl ethyl ether.

[0088] Suitable phosphorus compounds for forming the dispersants herein include any phosphorus compound or mixture of phosphorus compounds capable of introducing phosphorus-containing species into the ashless dispersant. Thus, either organic or inorganic phosphorus compounds capable of such a reaction can be used. Thus, such inorganic phosphorus compounds can be used as inorganic phosphoric acid and inorganic phosphorus oxides, including their hydrates. Typical organophosphorus compounds include full and partial esters of phosphoric acid, such as mono-, di-, and triesters of phosphoric, thiophosphoric, dithiophosphoric, trithiophosphoric, and tetrathiophosphoric acids; mono-, di-, and triesters of phosphoric, thiophosphoric, dithiophosphoric, and trithiophosphoric acids; trihydrocarbyl phosphine oxides; trihydrocarbyl phosphine sulfides; mono- and dihydrocarbyl phosphonates (RPO(OR′)(OR″), where R and R′ are hydrocarbyl and R″ is hydrogen or a hydrocarbyl group), and their mono-, di-, and trithio analogs; mono- and dihydrocarbyl phosphonites (RP(OR′)(OR″), where R and R′ are hydrocarbyl and R″ is hydrogen or a hydrocarbyl group), and their mono- and dithio analogs. Thus, such compounds may be, for example, phosphorous acid (H3PO3, sometimes represented as H2(HPO3) and sometimes called ortho-phosphorous acid or phosphonic acid), phosphoric acid (H3PO4, sometimes called orthophosphoric acid), hypophosphoric acid (H4P2O6), metaphosphoric acid (HPO3), pyrophosphoric acid (H4P2O7), hypophosphorous acid (H3PO2, sometimes called phosphinic acid), pyrophosphorous acid (H4P2O5, sometimes called pyrophosphonic acid), phosphinous acid (H3PO), tripolyphosphoric acid (H5P3O 10 ), tetrapolyphosphate (H5P4O 13 ), trimetaphosphoric acid (H3P3O9), phosphorus trioxide, phosphorus tetroxide, phosphorus pentoxide, etc. Phosphorotetrathioic acid (H3PS4), phosphoromonothioic acid (H3PO3S), phosphorodithioic acid (H3PO2S2), phosphorotrithioic acid (H3POS3), phosphorus sesquisulfide, phosphorus heptasulfide, and phosphorus pentasulfide (PS5, P4S 10Partial or all-sulfur analogs such as HCl, HCl (sometimes referred to as HCl), may also be used in forming dispersants for the present disclosure. Inorganic phosphorus halide compounds such as PCl, PBr, POCl, PSCl, etc. may also be used.

[0089] Similarly, organophosphorus compounds can be used, such as mono-, di-, and triesters of phosphoric acid (e.g., trihydrocarbyl phosphates, dihydrocarbyl monoacid phosphates, monohydrocarbyl diacid phosphates, and mixtures thereof), mono-, di-, and triesters of phosphorous acid (e.g., trihydrocarbyl phosphites, dihydrocarbyl hydrogen phosphites, hydrocarbyl diacid phosphites, and mixtures thereof), esters of phosphonic acid (both "primary", RP(O)(OR)2, and "secondary"). and full- or partial-sulfur analogs of any of the foregoing organophosphorus compounds, such as R2P(O)(OR)), esters of phosphinic acid, phosphonyl halides (e.g., R2P(O)Cl2 and R2P(O)Cl), halophosphates (e.g., R2P(O)Cl2 and (RO)2P(O)Cl), tertiary pyrophosphate esters (e.g., (RO)2P(O)-O-P(O)(OR)2), and full- or partial-sulfur analogs of any of the foregoing organophosphorus compounds, wherein each hydrocarbyl group contains up to about 100 carbon atoms, preferably up to about 50 carbon atoms, more preferably up to about 24 carbon atoms, and most preferably up to about 12 carbon atoms. Halophosphines (eg, hydrocarbyl phosphorus tetrahalides, dihydrocarbyl phosphorus trihalides, and trihydrocarbyl phosphorus dihalides) and halophosphines (monohalophosphines and dihalophosphines) can also be used.

[0090] The lubricants herein may comprise mixtures of one or more of the borated and phosphated dispersants described above in combination with non-boronated and non-phosphated dispersants.

[0091] When used, the dispersants described above provide a treat rate in the lubricant of from about 1 to about 5 weight percent, in other ways from about 1 to about 3 weight percent, and in other ways from about 1 to about 2 weight percent.

[0092] Antifoaming Agents: Antifoaming agents used to reduce or prevent the formation of stable foam include silicones, polyacrylates, or organic polymers. Foam suppressors that may be useful in the compositions of the present invention include polysiloxanes, copolymers of ethyl acrylate and 2-ethylhexyl acrylate, and optionally vinyl acetate. When present, the amount of antifoaming agent in the lubricating fluid may be up to 0.1 wt.%, up to 0.08 wt.%, or less than 0.07 wt.%, based on the total weight of the lubricating fluid.

[0093] Seal Swelling Agents: The fluids of the present disclosure may further include a seal swelling agent, such as an ester, adipate, sebacate, azealate, phthalate, sulfone, alcohol, alkyl benzene, substituted sulfolane, aromatic compound, or mineral oil, that causes swelling of elastomeric materials used as seals in various engines, motors, and transmissions.

[0094] Alcohol-based seal swelling agents are generally low-volatility linear alkyl alcohols such as decyl alcohol, tridecyl alcohol, and tetradecyl alcohol. Alkyl benzenes useful as seal swelling agents include dodecyl benzene, tetradecyl benzene, dinonyl-benzene, di(2-ethylhexyl)benzene, and the like. Substituted sulfolanes (such as those described in U.S. Pat. No. 4,029,588, incorporated herein by reference) are also useful as seal swelling agents in compositions according to the present invention. Mineral oils useful as seal swelling agents in the present disclosure include low-viscosity mineral oils with high naphthenic or aromatic content.

[0095] Pour Point Depressants: The lubricants described herein may optionally contain one or more pour point depressants. Suitable pour point depressants include esters of maleic anhydride-styrene, polymethacrylate, polymethyl methacrylate, polyacrylate, or polyacrylamide, or mixtures thereof. If present, the pour point depressant may be present in an amount of about 0.001 wt. % to about 0.04 wt. %, based on the total weight of the lubricant.

[0096] Generally, the durable lubricating fluids for electric or hybrid-electric motor applications described herein may contain additive components within the ranges listed in Table 2.

[0097] [Table 2]

[0098] The percentages of each component listed above represent the weight percent of each component, based on the total weight of the lubricating fluid including the listed component. The additives used in formulating the compositions described herein can be mixed into the base oil individually or in various subcombinations. However, it may be preferable to mix all of the components simultaneously using an additive concentrate (i.e., additives plus a diluent, such as a hydrocarbon solvent). The use of an additive concentrate takes advantage of the mutual compatibility afforded by the combination of components when in the form of an additive concentrate. The use of a concentrate also shortens mixing time and reduces the possibility of mixing errors. [Example]

[0099] The following non-limiting examples are provided to further illustrate the features and advantages of one or more embodiments of the present disclosure. Unless otherwise specified or apparent from the context of the discussion, all percentages, ratios, and parts set forth in the examples and elsewhere in this disclosure are by weight.

[0100] To demonstrate how the fluids selected herein exhibited the desired conductivity, exemplary finished fluids were formulated, aged, and evaluated.

[0101] In the following examples, several formulations were blended. For each formulation, a first lubricant sample was taken and initial electrical conductivity was measured at 1.5 volts, 20 Hz, and 160°C using an Epsilon+ electrical conductivity meter (Flucon Fluid Control GmbH) or equivalent instrument according to ASTM D2624-15 (modified to test lubricants rather than fuels) to obtain at least one conductivity reading. A second lubricant sample was then taken from each formulation and aged at 170°C for 192 hours according to CEC L-48-A-00. After aging, the fluid was allowed to cool to room temperature. After cooling, the conductivity of each aged fluid was measured using an Epsilon+ electrical conductivity meter (Flucon Fluid Control GmbH) or equivalent instrument at 1.5 volts, 20 Hz, and 160°C according to ASTM D2624-15 (modified to test lubricants rather than fuels) to obtain at least one conductivity reading for each aged fluid evaluated.

[0102] Example 1 All of the formulations tested in Table 3 below contained the same base additive package, including friction modifiers, detergents, antioxidants, phosphated and borated dispersants, corrosion inhibitors, and process oil. In addition to the base additive package, the formulations contained the additional additives listed in Table 3. The formulations had minor variations in process oil treat rate, ranging from about 1.75 to about 0.43 weight percent of the finished fluid, depending on the amount of thiadiazole or its derivatives and / or amine phosphate salts contained in the formulation. The formulations had a total additive treat rate of about 5 to about 5.5 weight percent and contained similar base oils and viscosity modifiers to achieve a kinematic viscosity at 100°C of between about 4.9 and 5.9 cSt.

[0103] The additives in Table 3 were evaluated for initial and aged conductivity to determine electrical conductivity durability, or the ability of the fluid to maintain a relatively low electrical conductivity after aging. Low conductivity durability is desired, meaning that the fluid maintains its conductivity performance as it ages. Table 3 reports the weight percent of thiadiazole and amine phosphate salt in the finished fluid, which also includes the additive package and base oil as reported above. The total sulfur, phosphorus, and nitrogen, as well as the ratios listed above, are calculated based on the amounts of such elements provided by the various components of the finished fluid. The conductivity results are shown in Table 4.

[0104] [Table 3]

[0105] [Table 4]

[0106] As shown in Figure 1, the effect of total fluid sulfur and phosphorus relative to total nitrogen on the fluid's conductivity durability (i.e., the absolute value of the initial conductivity at 160°C compared to the conductivity after aging at 160°C) is substantially improved for samples of the present invention having a ratio of 2.3 or greater and at least about 0.7 weight percent of thiadiazole in the fluid. This result is surprising at such levels of total fluid sulfur and phosphorus, given the tendency of these elements to be conductive. Furthermore, given the low molecular weight of the thiadiazole, the fluid's conductivity would have been expected to be unacceptably high after aging.

[0107] Although the lubricating compositions of the present disclosure have been described with reference to the Detailed Description and Abstract herein, it should be understood that the foregoing description is intended to illustrate, but not limit, the scope of the disclosure, which is defined by the appended claims. Other aspects, advantages, and modifications are within the scope of the claims. It is intended that the specification and examples be considered as exemplary only, with the true scope of the disclosure being indicated by the appended claims.

[0108] Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. As used throughout the specification and claims, "a" and / or "an" can refer to one or more than one. Unless otherwise indicated, all numbers expressing properties such as amounts, molecular weights, percentages, ratios of ingredients, reaction conditions, and the like used herein, whether or not the term "about" is present, should be understood in all instances to be modified by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0109] It is understood that each component, compound, substituent, or parameter disclosed herein should be construed as disclosed for use alone or in combination with one or more of any and all other components, compounds, substituents, or parameters disclosed herein.

[0110] It is further understood that each range disclosed herein should be construed as a disclosure of each specific value within the disclosed range having the same number of significant digits. Thus, a range of 1 to 4 should be construed as an explicit disclosure of any range of values ​​of 1, 2, 3, and 4, as well as 1 to 4, 1 to 3, 1 to 2, 2 to 4, 2 to 3, etc.

[0111] It is further understood that each lower limit of each range disclosed herein should be interpreted as disclosed in combination with each upper limit of each range and each specific value within each range for the same component, compound, substituent, or parameter. Accordingly, the present disclosure should be interpreted as a disclosure of all ranges derived by combining each lower limit of each range with each upper limit of each range, or with each specific value within each range, or by combining each upper limit of each range with each specific value within each range.

[0112] Furthermore, any specific amount / value of a component, compound, substituent, or parameter disclosed in the description or examples should be construed as disclosing either the lower or upper limit of a range and, therefore, can be combined with any other lower or upper limit of a range or specific amount / value for the same component, compound, substituent, or parameter disclosed elsewhere in this application to form a range for that component, compound, substituent, or parameter.

Claims

1. 1. A durable lubricating composition for an electric vehicle or a hybrid electric vehicle, comprising: a base oil of lubricating viscosity; at least 0.7 weight percent of a thiadiazole or a derivative thereof; an amine salt of a phosphoric acid ester providing at least 100 ppm of phosphorus to the durable lubricating composition; having a weight ratio of sulfur and phosphorus to nitrogen ((S+P) / N) of at least 2.3; at least 150 ppm phosphorus and at least 2000 ppm sulfur; and A durable lubricating composition for electric or hybrid electric vehicles having a conductivity durability of 50,000 pS / m or less.

2. 10. The durable lubricating composition for electric or hybrid electric vehicles of claim 1, wherein the thiadiazole is selected from a monohydrocarbyl thiol-substituted thiadiazole, a bishydrocarbyl thiol-substituted thiadiazole, or a combination thereof.

3. 2. The durable lubricating composition for electric or hybrid electric vehicles of claim 1, wherein the thiadiazole is 1,3,4-thiadiazole or a derivative thereof.

4. 10. The durable lubricating composition for electric or hybrid electric vehicles of claim 1, wherein the thiadiazole provides the durable lubricating composition with at least 2000 ppm sulfur.

5. 5. The durable lubricating composition for electric or hybrid electric vehicles of claim 4, wherein the durable lubricating composition comprises a maximum of 3500 ppm total sulfur and a maximum of 300 ppm total phosphorus, and / or the lubricating composition comprises 1 weight percent or less of the thiadiazole or derivative thereof.

6. The thiadiazole or derivative thereof comprises one or more compounds having the structure of Formula I: 【Chemistry 1】 During the ceremony, Each R １ are independently hydrogen or sulfur; Each R ２ are independently an alkyl group; n is an integer of 0 or 1, and R １ is hydrogen, the adjacent R ２ The integer n in the moiety is 0, and R １ is sulfur, the adjacent R ２ said n in the moiety is 1; At least one R １ 10. The durable lubricating composition for electric or hybrid electric vehicles of claim 1, wherein is sulfur.

7. 10. The durable lubricating composition for electric or hybrid electric vehicles of claim 1, wherein the amine salt of a phosphate ester comprises one or more mono- and / or di-alkyl phosphate esters, wherein the alkyl groups can be linear or branched.

8. The amine salt of a phosphoric acid ester is represented by Formula II: 【Chemistry 2】 During the ceremony, R ３ and R ４ may independently be hydrogen or a linear, branched, or cyclic hydrocarbyl group; m is an integer from 0 to 1, p is an integer from 1 to 2, and m+p is equal to 2; R ５ , R ６ , R ７ , and R ８ may independently be hydrogen or a hydrocarbyl group, and R ５ ~R ８ 8. The durable lubricating composition for electric or hybrid electric vehicles of claim 7, wherein at least one of: is a hydrocarbyl group.

9. R ３ and R ４ may independently be a C3-C10 alkyl group, and / or R ５ , R ６ , R ７ , and R ８ 9. The durable lubricating composition for electric or hybrid electric vehicles of claim 8, wherein at least one of: is a C10 to C20 alkyl group.

10. R ５ , R ６ , R ７ , and R ８ 10. The durable lubricating composition for electric or hybrid electric vehicles of claim 9, wherein two of are independently a C10 to C20 alkyl group.

11. 10. The durable lubricating composition for electric or hybrid electric vehicles of claim 1, wherein the amine salt of a phosphoric acid ester provides 40 to 90 weight percent of the total phosphorus in the durable lubricating composition.

12. 12. The durable lubricating composition for electric or hybrid electric vehicles of claim 11, wherein the thiadiazole or derivative thereof provides at least 99 weight percent of the total sulfur in the durable lubricating composition.

13. 10. The durable lubricating composition for electric or hybrid electric vehicles of claim 1, wherein the lubricating composition comprises 0.25 to 0.5 weight percent of the amine salt of a phosphate ester.

14. 10. The durable lubricating composition for electric or hybrid electric vehicles of claim 1, wherein the lubricating composition has an initial electrical conductivity before aging of 150,000 or less when measured at 1.5 volts, 20 Hz, and 160°C according to ASTM D2624-15.

15. 10. The durable lubricating composition for electric or hybrid electric vehicles of claim 1, wherein the conductivity durability is the difference between the initial conductivity and the final conductivity, the initial and final conductivity being measured at 1.5 volts, 20 Hz, and 160°C in accordance with ASTM D2624-15, and the final conductivity being measured after the lubricating composition has been aged at 170°C for 192 hours in accordance with CEC L-48-A-00.

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