Low viscosity lubrication fluid for electric motor system

Abstract

To provide an electric motor lubrication fluid that achieves acceptable wear and friction performance and maintains oxidation stability, while ensuring lubricant compatibility with electrically charged components in a powertrain.SOLUTION: An electric motor lubrication fluid for an electric motor system comprises a lubricant base oil, at least one sulfurized component, at least two phosphorus-providing additives, and at least one high-molecular-weight dispersant.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a lubricating fluid for an electric motor system and a method of lubricating gears and clutches within an electric motor system. In particular, the disclosed method and lubricating fluid relate to a low viscosity lubricating fluid for use in an electric motor of an electric vehicle or a hybrid electric vehicle, comprising an oil of lubricating viscosity and at least one higher molecular weight dispersant.

Background Art

[0002] A major challenge in developing lubricants for electric vehicle powertrains is to achieve acceptable wear and friction performance and maintain oxidative stability while ensuring lubricant compatibility with charged components in the powertrain. Lubricants in electric vehicles or hybrid electric vehicles can also come into contact with components within the electric motor, so the electrical conductivity of the fluid also needs to be relatively low to prevent electrostatic accumulation and discharge of charged components.

[0003] To improve efficiency, lubricant manufacturers often attempt to reduce the viscosity of lubricants. However, lower viscosity fluids are often less desirable for the severe wear and friction tests often required by industrial and / or automotive manufacturers. Thus, low viscosity fluids may often require additional anti-wear additives to meet the required wear tests. However, adding these additional additives often increases the electrical conductivity of the lubricant and decreases its oxidation stability. For example, lubricants having a kinematic viscosity of about 4.5 cSt or less at 100 °C (ASTM D445) may require more anti-wear additive than is required in higher viscosity lubricants to achieve the required wear performance, but the addition of certain anti-wear additives can result in increased conductivity and decreased oxidation stability. In particular, while low viscosity lubricants having a kinematic viscosity of about 4.5 cSt or less, or 3.5 cSt or less, or 3.0 cSt or less at 100 °C pass severe FZG wear tests such as the demanding A10 / 16.6R / 90 scuffing test of CEC L-84-02, they also exhibit low conductivity and have previously been difficult to maintain oxidation stability. SUMMARY OF THE INVENTION

[0004] In one embodiment, an electric motor lubricating fluid suitable for an electric vehicle or a hybrid electric vehicle is described herein. In the method, the electric motor lubricating fluid is one or more base oils of lubricating viscosity and a succinimide dispersant derived from polyisobutylene having a number average molecular weight of about 2,000 or more, having about 0.5 to about 1 wt% nitrogen, post-treated with a phosphorus-containing compound and a boron-containing compound, and delivering about 70 to about 140 ppm of phosphorus and about 150 to about 300 ppm of nitrogen to the electric motor lubricating fluid, a succinimide dispersant, an amine salt of a phosphate ester providing about 40 to 70 ppm of phosphorus to the electric motor lubricating fluid, an oil-soluble phosphorus antiwear additive including an ashless dialkyldithiophosphate providing about 40 to about 70 ppm of phosphorus to the electric motor lubricating fluid, and a sulfur-providing additive including a thiadiazole or a derivative thereof providing up to about 950 ppm of sulfur to the electric motor lubricating fluid, and the electric motor lubricating fluid has a kV100°C of about 4.5 cSt or less and a total phosphorus of about 150 to about 250 ppm.

[0005] In other methods or embodiments, the electric motor lubrication described in the preceding paragraph may include one or more optional features or embodiments in any combination. These optional features or embodiments may include one or more of the following: The amine salt of the phosphate ester has a structure of Formula I or a solvate or hydrate thereof,

[0006]

Chemical formula

[0007] [Chemical formula] R 7 and R 8 are independently C 3 ~C 8 linear or branched alkyl groups, R9 is -H or -CH 3 and / or the ashless dialkyldithiophosphate is 3 - [[bis(2 - methylpropoxy)phosphinothioyl]thio]-2 - methyl - propanoic acid, and / or the thiadiazole or its derivative contains one or more compounds having the structure of formula III,

[0008]

Chemical formula

[0009] In still other embodiments, the present disclosure provides an additive concentrate suitable for an electric motor lubricating fluid. In one approach, the additive concentrate is a succinimide dispersant derived from high - molecular - weight polyisobutylene having a number - average molecular weight of about 2,000 or more, having about 0.5 to about 1 wt% nitrogen, post - treated with a phosphorus - containing compound and a boron - containing compound, and present in an amount that delivers about 1400 to about 2450 ppm of phosphorus and about 3000 to about 5400 ppm of nitrogen to the dispersant additive concentrate, a succinimide dispersant, an amine salt of a phosphate ester that provides about 1000 - 1500 ppm of phosphorus to the additive concentrate, an oil - soluble phosphorus anti - wear additive containing an ashless dialkyldithiophosphate that provides about 800 ppm to about 1300 ppm of phosphorus to the additive concentrate, and a sulfur - providing additive containing a thiadiazole or its derivative that provides sulfur but provides about 18,000 ppm or less of sulfur to the additive concentrate, and the additive concentrate has a kV100°C of about 15 cSt to about 80 sCt.

[0010] In other embodiments, the additive concentrate of the preceding paragraph may include one or more optional features or embodiments in any combination. These optional features or embodiments may include one or more of the following: The amine salt of the phosphate ester has the structure of Formula I or a solvate or hydrate thereof,

[0011]

Chemical formula

[0012]

Chemical formula

[0013]

Chemical formula

[0014] In yet other embodiments, a method for lubricating drive train components including an electric motor is also described herein. In the method, the method includes lubricating the drive train components with an electric motor lubricating composition, the electric motor lubricating composition contacting a portion of the electric motor, and the electric motor lubricating composition comprising: (i) one or more base oils of lubricating viscosity; (ii) a succinimide dispersant derived from a high molecular weight polyisobutylene having a number average molecular weight of about 2,000 or greater, the succinimide dispersant having from about 0.5 to about 1 weight percent nitrogen, post-treated with a phosphorus-containing compound and a boron-containing compound, and delivering from about 70 to about 140 ppm phosphorus and from about 150 to about 300 ppm nitrogen to the electric motor lubricating fluid; (iii) an amine salt of a phosphate ester providing from about 40 to 70 ppm phosphorus to the electric motor lubricating fluid; (iv) an oil-soluble phosphorus antiwear additive comprising a zinc dialkyldithiophosphate providing from about 40 to about 70 ppm phosphorus to the electric motor lubricating fluid; and (v) a sulfur-providing additive comprising a thiadiazole or a derivative thereof providing sulfur to the electric motor lubricating fluid, but providing 950 ppm or less sulfur, wherein the electric motor lubricating fluid has a kV100°C of about 4.5 cSt or less, a total phosphorus of from about 150 to about 250 ppm, and an electrical conductivity of about 37 nS / M or less, as measured by a modified conductivity test conducted in accordance with ASTM D2624-15 using the electric motor lubricating fluid and measured at 20 Hz and 100°C.

[0015] In further embodiments, the method for lubricating drive train components including the electric motor of the preceding paragraph can further include any combination of one or more optional method steps, features, or embodiments. These optional method steps, features, or embodiments can include one or more of the following: the amine salt of the phosphate ester has a structure of Formula I or a solvate or hydrate thereof,

[0016]

Chemical formula

[0017]

Chem.

[0018]

Chem.

[0019] In yet another embodiment, the present disclosure provides for the use of an additive concentrate in an electric motor lubricating composition and / or the use of an electric motor lubricating composition to achieve a kV100°C of about 4.5 cSt or less in an electric motor lubricating composition having a total phosphorus of about 150 to about 250 ppm and an electrical conductivity of about 37 nS / M or less, as measured by a modified conductivity test in accordance with ASTM D2624-15 using an electric motor lubricating fluid and measured at 20 Hz and 100°C. In other embodiments, the use comprises (i) one or more base oils of lubricating viscosity, (ii) a succinimide dispersant derived from a high molecular weight polyisobutylene having a number average molecular weight of about 2,000 or greater, having about 0.5 to about 1 weight % nitrogen, post-treated with a phosphorus-containing compound and a boron-containing compound, and delivering about 70 to about 140 ppm phosphorus and about 150 to about 300 ppm nitrogen to the electric motor lubricating fluid, (iii) an amine salt of a phosphate ester providing about 40 to 70 ppm phosphorus to the electric motor lubricating fluid, (iv) an oil-soluble phosphorus antiwear additive comprising an ashless dialkyldithiophosphate providing about 40 to about 70 ppm phosphorus to the electric motor lubricating fluid, and (v) a sulfur-providing additive comprising a thiadiazole or derivative thereof providing sulfur to the electric motor lubricating fluid but providing about 950 ppm or less sulfur. In yet another approach or embodiment, the use may also include any other embodiment of the electric motor lubricating composition, any other embodiment of the method, or any other embodiment of the additive concentrate, as described above in this summary.

[0020] Other embodiments of the present disclosure will be apparent to those of ordinary skill in the art in view of the specification and practice of the invention disclosed herein.

[0021] The following definitions are provided to clarify the meaning of specific terms used herein.

[0022] The terms "lubricating oil", "lubricant composition", "lubricating composition", "lubricant", and "lubricating and cooling fluid" refer to finished lubricating products that contain a major amount of base oil and a minor amount of additive composition.

[0023] As used herein, the terms "additive package", "additive concentrate", and "additive composition" refer to the portion of a lubricating oil composition excluding the majority of the base oil.

[0024] As used herein, the term "hydrocarbyl substituent" or "hydrocarbyl group" is used in its ordinary meaning well known to those skilled in the art. Specifically, it refers to a group that has a carbon atom directly bonded to the remainder of the molecule and that has predominantly hydrocarbon character. Each hydrocarbyl group is independently selected from hydrocarbon substituents, and substituted hydrocarbon substituents contain one or more of halo groups, hydroxyl groups, alkoxy groups, mercapto groups, nitro groups, nitroso groups, amino groups, pyridyl groups, furyl groups, imidazolyl groups, oxygen, and nitrogen, and two or fewer non-hydrocarbon substituents are present per ten carbon atoms in the hydrocarbyl group.

[0025] As used herein, the term "percent by weight" or "wt%" means, unless otherwise indicated, the percentage that the listed component represents relative to the total weight of the composition.

[0026] The terms "soluble", "oil-soluble", or "dispersible" as used herein may indicate that a compound or additive is soluble, miscible, or suspendable in oil at all ratios, but not necessarily so. However, the foregoing terms mean that they are soluble, suspendable, miscible, or stably dispersible in oil to an extent sufficient to perform their intended effects, for example, in an environment where oil is used. Further, if desired, it may be possible to incorporate higher levels of specific additives by further incorporating other additives.

[0027] As used herein, the term "alkyl" refers to a straight-chain, branched-chain, cyclic, and / or substituted saturated chain moiety of from about 1 to about 200 carbon atoms.

[0028] As used herein, the term "alkenyl" refers to a straight-chain, branched-chain, cyclic, and / or substituted saturated chain moiety of from about 3 to about 30 carbon atoms.

[0029] As used herein, the term "aryl" refers to monocyclic and polycyclic aromatic compounds that may contain alkyl, alkenyl, alkylaryl, amino, hydroxyl, alkoxy, halo substituents, and / or heteroatoms, such as, but not limited to, nitrogen and oxygen.

[0030] As used herein, "number average molecular weight" or "Mn" is determined by gel permeation chromatography (GPC) using commercially available polystyrene standards having an Mn of from about 180 to about 18,000 as a calibration standard.

[0031] Throughout this disclosure, terms such as "comprises," "includes," "contains," etc. are considered to be open-ended and are to be understood to include any element, step, or ingredient not explicitly listed. The phrase "consisting essentially of" means including any explicitly listed element, step, or ingredient, and any additional element, step, or ingredient that does not materially affect the basic and novel aspects of the invention. This disclosure also contemplates that any composition described using the terms "comprises," "includes," "contains" should be construed to include the disclosure of the same composition "consisting essentially of" or "consisting of" its specifically listed components.

DETAILED DESCRIPTION OF THE INVENTION

[0032] According to an exemplary embodiment, there is provided an electric motor lubricating fluid suitable for an electric vehicle or a hybrid electric vehicle, which has a low viscosity at kV100°C of about 4.5 cSt or less, about 3.5 cSt or less, or about 3.0 cSt or less, and can still pass stringent FZG scuffing tests such as the A10 / 16.6R / 90 test of CEC L-84-02, while achieving good electrical conductivity and maintaining oxidation stability. However, surprisingly, for the lubricating fluids herein, it has been found that a specific combination of additives including a succinimide dispersant derived from relatively high molecular weight polyisobutylene is useful for achieving acceptable wear, conductivity, and oxidation performance. The selected relatively high molecular weight dispersant described herein results in an additive concentrate having a relatively high viscosity when incorporated into the additive concentrate. Such high viscosity additive concentrates have not been used heretofore in low viscosity finished lubricants (e.g., finished lubricants having a kV100°C of about 4.5 cSt or less, about 3.5 cSt or less, or about 3.0 cSt or less) that require strict wear protection, low conductivity, and oxidation stability.

[0033] It was not expected that a relatively high viscosity additive concentrate having a relatively high molecular weight succinimide dispersant would be suitable for forming a low viscosity finished lubricant that can pass the wear, conductivity, and oxidation performance tests of electric vehicles and / or hybrid electric vehicles. However, when the selected relatively high molecular weight succinimide dispersant herein is combined with other lubricant additives having specific elemental relationships to form a finished lubricant, the finished lubricant herein achieves low viscosity, acceptable scuffing performance, appropriate conductivity, and oxidation stability for a drive system having an electric motor or a hybrid electric motor.

[0034] Relatively high molecular weight polyisobutylene dispersants, when such high molecular weight dispersants are also provided in a specific amount in the final fluid in combination with a selected amount of phosphorus, nitrogen, and / or sulfur from other additives such as amine salts of phosphate esters, ashless dialkyldithiophosphates, and thiadiazoles or their derivatives, can be provided for fluids for such electrical or hybrid electrical applications having a low final fluid viscosity, as found herein. In one approach, for example, the fluid described herein is (i) a succinimide dispersant derived from polyisobutylene having a number average molecular weight of about 2,000 or greater, having up to about 1 wt% nitrogen, and post-treated with a phosphorus-containing compound and a boron-containing compound, delivering about 60 to about 120 ppm of phosphorus and about 150 to about 300 ppm of nitrogen to an electric motor lubricating fluid, (ii) an amine salt of a phosphate ester providing about 45 to 75 ppm of phosphorus to the electric motor lubricating fluid, (iii) an oil-soluble phosphorus antiwear additive comprising an ashless dialkyldithiophosphate providing about 40 to about 70 ppm of phosphorus to the electric motor lubricating fluid, and (iv) a sulfur-providing additive comprising a thiadiazole or its derivative that provides sulfur to the lubricant but provides up to about 950 ppm of sulfur to the electric motor lubricating fluid, and the electric motor lubricating fluid has a kV100℃ of about 4.5 cSt or less, about 3.5 cSt or less, about 3.0 cSt or less (ASTM D4450), a total phosphorus of about 150 to about 250 ppm, and an electrical conductivity of about 60 nS / M or less, measured by a modified conductivity test in accordance with ASTM D2624-15 using the electric motor lubricating fluid and measured at about 20 Hz and about 100℃. In still other embodiments, the lubricants described herein may also include an amount of calcium from a detergent additive (e.g., up to about 50 ppm of calcium in the lubricant, or up to about 950 ppm of calcium in the additive concentrate of a neutral to low basicity detergent). Further description of the additives for each component is provided below.

[0035] Succinimide Dispersant: The lubricating fluid for an electric motor of this specification contains a dispersant system having at least one oil-soluble ashless dispersant, which is a succinimide dispersant derived from a relatively high molecular weight polyisobutylene having a number average molecular weight of about 2000 or more and is post-treated with a phosphorus-containing compound and a boron-containing compound. Such a relatively high molecular weight succinimide dispersant results in a dispersant additive concentrate having a kV100°C of about 15 to about 80 cSt (ASTM D445) at an appropriate treatment rate. The succinimide dispersant of this specification can be derived from a relatively high molecular weight hydrocarbyl-substituted dicarboxylic acid or anhydride reacted with a polyalkylene polyamine. The succinimide dispersants and their preparation are disclosed in at least U.S. Patent No. 7,897,696 and / or U.S. Patent No. 4,234,435, which are incorporated herein by reference.

[0036] The relatively high molecular weight hydrocarbyl moiety of the hydrocarbyl-dicarboxylic acid or its anhydride can be derived from a butene polymer, for example, a polymer of isobutylene. Suitable polyisobutylenes for use herein include those formed from polyisobutylene or a highly reactive polyisobutylene having a terminal vinylidene content of at least about 60%, such as about 70% to about 90% or more. Suitable polyisobutylenes include those prepared using a BF 3 catalyst.

[0037] The dispersants of the present specification have a relatively high molecular weight. Thus, the number average molecular weight of the polyisobutylene substituents of the dispersants of the present specification can vary from at least about 2,000 to, in some cases, up to about 3,000 as determined by gel permeation chromatography (GPC) using polystyrene (having a number average molecular weight of 180 to about 18,000) as a calibration standard. The GPC method further provides average weight molecular weight distribution information. See also, 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 incorporated herein by reference.

[0038] The polyisobutylene moiety in the dispersants of the present specification may also preferably have a molecular weight distribution (MWD), also referred to as the polydispersity index, determined by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). In some methods or embodiments, a suitable polyisobutylene moiety may have an Mw / Mn of less than about 3.0, or less than about 2.8, or less than about 2.5. In other methods, suitable polyisobutylene substituents have a polydispersity of about 1.5 to about 3.0, or about 2.0 to about 3.0.

[0039] Dicarboxylic acids or anhydrides suitable for forming the dispersant include maleic anhydride, maleic acid, fumaric acid, malic acid, tartaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, mesaconic acid, ethyl maleic acid anhydride, dimethyl maleic acid anhydride, ethyl maleic acid, dimethyl maleic acid, hexyl maleic acid, etc., the corresponding acid halides and C 1 ~C 4It can be selected from carboxylic acid reactants containing aliphatic esters. In some processes, the molar ratio of dicarboxylic acid or anhydride to hydrocarbyl moiety in the reaction mixture used to make the hydrocarbyl dicarboxylic acid or anhydride can vary widely. Thus, the charge molar ratio can vary from 5:1 to 1:5, such as from 3:1 to 1:3. In some embodiments, particularly suitable molar ratios of acid or anhydride to hydrocarbyl moiety are less than 1:1 to 1.6:1. In other embodiments, another useful charge molar ratio of dicarboxylic acid or anhydride to hydrocarbyl moiety can be 1:1 to 1.5:1, or 1:1 to 1.4:1, or 1.1:1 to 1.3:1, or 1:1 to 1.2:1.

[0040] Any of a number of polyalkylene polyamines can be used in the preparation of the dispersant additives of this specification. Non-limiting exemplary polyamines include aminoguanidine bicarbonate (AGBC), diethylene triamine (DETA), triethylene tetramine (TETA), tetraethylene pentamine (TEPA), pentaethylene hexamine (PEHA), and heavy polyamines. Heavy polyamines have a small amount of polyamine oligomers such as TEPA and PEHA, but mainly have oligomers with 7 or more nitrogen atoms and 2 or more primary amines per molecule, and can include mixtures of polyalkylene polyamines having a wider range of branching than conventional polyamine mixtures. Typically, these heavy polyamines have an average of 6.5 nitrogen atoms per molecule. Further non-limiting polyamines that can be used to prepare hydrocarbyl-substituted succinimide dispersants are disclosed in U.S. Patent No. 6,548,458, the entire disclosure of which is incorporated herein by reference. In some embodiments, the charge molar ratio of the hydrocarbyl dicarboxylic acid or anhydride to the polyalkylene polyamine can be from about 1:1 to about 3.0:1. In one embodiment, the dispersant in the present disclosure described herein can be a reaction product of polyisobutene succinic anhydride (PIBSA) and a polyamine, such as a heavy polyamine having a charge molar ratio of polyisobutenyl-substituted succinic anhydride to the polyamine of from about 1.7:1 to about 2.5:1.

[0041] As described above, the high molecular weight succinimide dispersant of the present invention can be post-treated with a boron compound. Suitable boron compounds useful for forming the dispersant herein include any boron compound or mixture of boron compounds capable of introducing boron-containing species into an 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, HBF 4 boric acids, such as boronic acids (e.g., alkyl-B(OH) 2 , or aryl-B(OH) 2 ), boric acid (i.e., H 3 BO 3 ), tetraboric acid (i.e., H 2 B 5 O 7 ), metaboric acid (i.e., HBO 2 ), 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 boron reactants 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.

[0042] The high molecular weight succinimide dispersant of the present invention can also be post-treated with a phosphorus compound. Suitable phosphorus compounds for forming the dispersant in this specification include phosphorus compounds or mixtures of phosphorus compounds capable of introducing phosphorus-containing species into an ashless dispersant. Therefore, any organic or inorganic phosphorus compound capable of undergoing such a reaction can be used. Thus, such an inorganic phosphorus compound can be used as an inorganic phosphorus oxide containing inorganic phosphoric acid and its hydrates. Typical organic phosphorus compounds include complete esters and partial esters of phosphoric acid such as mono-, di-, and triesters of phosphoric acid, thiophosphoric acid, dithiophosphoric acid, trithiophosphoric acid, and tetrathiotriphosphoric acid; mono-, di-, and triesters of phosphorous acid, thiophosphorous acid, dithiophosphorous acid, and trithiophosphorous acid; trihydrocarbylphosphine oxide; trihydrocarbylphosphine sulfide; mono- and dihydrocarbylphosphonates, (RPO(OR’)(OR”) (wherein R and R’ are hydrocarbyls and R” is a hydrogen atom or a hydrocarbyl group), and their mono-, di-, and trithio analogs; mono- and dihydrocarbylphosphinites, (RP(OR’)(OR”) (wherein R and R’ are hydrocarbyls and R” is a hydrogen atom or a hydrocarbyl group), and their mono- and dithio analogs, and the like. Therefore, such compounds can be, for example, phosphorous acid (H 3 PO 3 , H 2 (HPO 3 ) which may also be represented as or sometimes called orthophosphorous acid or phosphoric acid), phosphoric acid (H 3 PO 4 , sometimes called orthophosphoric acid), hypophosphorous acid (H 4 P 2 O 6 ), metaphosphoric acid (HPO 3 ), pyrophosphoric acid (H 4 P 2 O 7 ), hypophosphorous acid (H 3 PO 2 , sometimes called phosphinic acid), pyrophosphorous acid (H 4 P 2 O 5, also sometimes called pyrophosphonic acid), phosphorous acid (H 3 PO), tripolyphosphoric acid (H 5 P 3 O 10 ), tetrapolyphosphoric acid (H 5 P 4 O 13 ), trimetaphosphoric acid (H 3 P 3 O 9 ), phosphorus trioxide, phosphorus tetroxide, phosphorus pentoxide, etc. can be used. Phosphorotetrathioic acid (H 3 PS 4 ), phosphoromonothioic acid (H 3 PO 3 S), phosphorodithioic acid (H 3 PO 2 S 2 ), phosphorotrithioic acid (H 3 POS 3 ), sesquisulfide of phosphorus, heptasulfide of phosphorus, and pentasulfide of phosphorus (P 2 S 5 , P 4 S 10 , also sometimes called) and other partial or total sulfur analogs can also be used for the formation of the dispersant for the present disclosure. PCl 3 , PBr 3 , POCl 3 , PSCl 3 and other inorganic phosphorus halide compounds can also be used.

[0043] Similarly, organic phosphorus compounds, for example, mono-, di-, and triesters of phosphoric acid (e.g., trihydrocarbyl phosphate, dihydrocarbyl monoacid phosphate, monohydrocarbyl diacid phosphate, and mixtures thereof), mono-, di-, and triesters of phosphorous acid (e.g., trihydrocarbyl phosphite, dihydrocarbyl hydrogen phosphite, hydrocarbyl diacid phosphite, and mixtures thereof), esters of phosphonic acid (both "primary" RP(O)(OR) 2 , and "secondary" R 2 P(O)(OR)), esters of phosphinic acid, phosphonyl halides (e.g., RP(O)Cl 2 and R2 P(O)Cl), halophosphates (e.g., (RO)PCl 2 and (RO) 2 PCl), halophosphites (e.g., ROP(O)Cl 2 and (RO) 2 P(O)Cl), tertiary pyrophosphate esters (e.g., (RO) 2 P(O)-O-P(O)(OR) 2 ), and any fully sulfur analogs or partial sulfur analogs of the aforementioned organophosphorus compounds, etc. can be used, and each hydrocarbyl group contains up to 100 carbon atoms, preferably up to 50 carbon atoms, more preferably up to 24 carbon atoms, and most preferably up to 12 carbon atoms. Halogenated halophosphines (e.g., tetrahalogenated hydrocarbylphosphines, trihalogenated dihydrocarbylphosphines, and dihalogenated trihydrocarbylphosphines), and halophosphines (monohalophosphines and dihalophosphines) can also be used.

[0044] In one embodiment, the relatively high molecular weight succinimide dispersant of the fluid herein contains at least a polyisobutenyl moiety having a number average molecular weight of at least about 2000, in other approaches about 2000 to about 3000, or in yet another approach about 2000 to about 2300, and has about 0.5 to about 1 wt% nitrogen, about 0.05 to about 0.25 wt% boron, and about 0.20 to about 0.45 wt% phosphorus, or in yet another embodiment, contains at least a polyisobutenyl moiety having a number average molecular weight of 2000 to 2300, and has about 0.60 to about 0.90 wt% nitrogen, about 0.10 to about 0.20 wt% boron, and about 0.25 to about 0.40 wt% phosphorus.

[0045] In some embodiments, the relatively high molecular weight dispersants described herein may constitute from about 40 to about 70 weight percent of the additive concentrate. In some embodiments, the relatively high molecular weight succinimide dispersants described herein include at least a polyisobutenyl moiety having a number average molecular weight of about 2000 to about 2300, and have about 0.6 to about 0.9 weight percent nitrogen, about 0.10 to about 0.20 weight percent boron, and about 0.25 to about 0.40 weight percent phosphorus, and may constitute from about 40 to about 70% of the additive concentrate. In some embodiments, the relatively high molecular weight succinimide dispersants described herein include at least a polyisobutenyl moiety having a number average molecular weight of about 2000 to about 2300, and deliver about 3000 to about 5400 ppm nitrogen, about 600 to about 1000 ppm boron, and about 1400 to about 2450 ppm phosphorus to the additive concentrate.

[0046] In some embodiments, the relatively high molecular weight dispersants described herein include from about 2.0 to about 4.0% of the electric motor lubricating fluid and deliver about 150 to about 300 ppm nitrogen, about 70 to about 140 ppm phosphorus, and about 30 to about 60 ppm boron. As shown in the following examples, when such succinimide dispersants are combined with other fluid components, particularly selected amounts of sulfur, boron, nitrogen, and / or phosphorus, the lubricant achieves good wear performance, conductivity performance, and oxidation stability.

[0047] Amine salt of phosphate ester: The electric motor lubricating fluid of the present specification also contains a first phosphorus-providing additive in an amount that provides about 40 to about 70 ppm of phosphorus from the amine salt to the fluid. In some methods or embodiments, the first phosphorus-providing additive is in the form of an amine salt of a phosphate ester. In some methods, examples of amine salts of phosphate esters include one or more monoalkyl phosphate esters, dialkyl phosphate esters, and / or mixtures thereof, and these alkyl groups can be linear, branched, or cyclic. The fluid of the present specification may also contain other compounds that provide phosphorus, but in some embodiments, the amine salt of the phosphate ester of the present specification provides about 20 to about 40% by weight of the total phosphorus in the electric motor lubricating fluid.

[0048] In some methods or embodiments, an exemplary amine salt of a phosphate ester can be represented by Formula I,

[0049] [Chemical Formula] R in Formula I 3 and R 4 can each independently be hydrogen or a linear, branched, or cyclic hydrocarbyl group, m in Formula I is an integer from 0 to 1, p in Formula I is an integer from 1 to 2, m + p is equal to 2, and R 5 in Formula I, R 6 in Formula I, R 7 and R 8 in Formula I can each independently be hydrogen or a hydrocarbyl group, and at least one of R 5 to R 8 in Formula I is a hydrocarbyl group. Examples of suitable alkyl or hydrocarbyl groups for R 3 and / or R 4 in Formula I include, but are not limited to, linear or branched alkyl groups such as propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and / or decyl groups. In yet another exemplary method, R 3 and R 4can be a cyclic hydrocarbyl group, and examples include cyclopentyl, cyclohexyl, cycloheptyl, methylcyclopentyl, dimethylcyclopentyl, methylcyclopentyl, dimethylcyclopentyl, methylethylcyclopentyl, diethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, methylethylcyclohexyl, diethylcyclohexyl, methylcycloheptyl, dimethylcycloheptyl, methylethyl - cycloheptyl, and / or diethylcycloheptyl. In some methods or embodiments, a suitable amine salt of the phosphate ester is a mixture of monoalkyl and dialkyl phosphate esters. The monoalkyl and dialkyl groups can be linear, branched, or cyclic as described above.

[0050] The amine salt of the phosphate ester can be derived from a primary, secondary, or tertiary amine, or a mixture thereof. Exemplary amines suitable for the salt 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, and 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. Secondary amines can also be cyclic amines such as piperidine, piperazine, and morpholine. Examples of suitable tertiary amines can include tri - n - butylamine, tri - n - octylamine, tri - decylamine, tri - laurylamine, tri - hexadecylamine, and / or dimethyl - oleylamine.

[0051] In some methods, the amine of formula I above is C 10~C 20 R which is an alkyl group 5 、R 6 、R 7 or R 8 may have at least one of the groups, and in other methods or embodiments, R of formula I 5 、R 6 、R 7 or R 8 at least two of the groups are, independently, C 10 ~C 20 alkyl group. In some embodiments, R of formula I 5 、R 6 、R 7 or R 8 at least two of the groups are, independently, C 12 ~C 14 alkyl group.

[0052] The amine salt of the phosphate ester can be prepared by reacting a suitable phosphorus compound with an amine to form the amine salt of the phosphate ester. In one embodiment, the amine salt of the phosphate ester may be of formula I, wherein R 3 and R 4 may independently be C 6 or hydrogen, m is an integer from 0 to 1, p is an integer from 1 to 2, m + p is equal to 2, R 5 、R 6 、R 7 and R 8 are independently hydrogen or a hydrocarbyl group of C 12 ~C 14 and at least one of R 5 ~R 8 is a hydrocarbyl group of C 12 ~C 14 .

[0053] In some embodiments, the amine salt of the phosphate ester may be present in the additive concentrate in an amount of 2 wt% to about 3 wt% or about 2.2 wt% to about 2.5 wt%. The amine salt of the phosphate ester can deliver about 1000 to about 1500 ppm of phosphorus or about 1000 to about 1250 ppm of phosphorus to the additive concentrate.

[0054] In the method, the amine salt of the phosphate ester can be present in the electric motor lubricating fluid of the present specification in an amount of at least about 0.1 wt% to about 0.3 wt%, or about 0.1 to about 0.25 wt% of the lubricating composition. The amine salt of the phosphate ester can deliver about 50 to about 150 ppm of phosphorus or about 50 to about 125 ppm of phosphorus to the lubricating composition.

[0055] Ashless dialkyldithiophosphate: In a method or embodiment, the electric motor lubricating fluid of the present specification may also include a second phosphorus-providing additive in the form of an acidic thiophosphate or a thiophosphate ester. In one method or embodiment, this second phosphorus-providing additive can be an ashless and amine-free dialkyldithiophosphate ester or a sulfur-containing phosphate ester.

[0056] The acidic thiophosphate, thiophosphate ester, or sulfur-containing phosphate ester of the second phosphorus compound can have one or more sulfur-phosphorus bonds. In one embodiment, the sulfur-containing phosphate ester can be an acidic thiophosphate, a thiophosphate ester, a thiophosphoric acid, or a salt thereof. The thiophosphate ester can be a dithiophosphate ester. In some more specific approaches, the acidic thiophosphate or thiophosphate ester can have the structure of Formula II or a salt thereof,

[0057]

Chemical formula

[0058]

Chemical formula

[0059] In some methods, an oil-soluble phosphorus antiwear additive containing an ashless dialkyldithiophosphate is prepared by a process comprising: (a) reacting an organic hydroxy compound with phosphorus pentasulfide (in some forms, a monomer or its dimer) to form a reaction product; and further reacting the reaction product with an unsaturated carboxylic acid to form an oil-soluble phosphorus antiwear additive containing an ashless dialkyldithiophosphate.

[0060] Suitable organic hydroxy compounds can include normal straight-chain alcohols, branched-chain alcohols, hydroxyaryl compounds such as phenol and naphthol, substituted aryl hydroxy compounds such as diamyl phenol, or any other hydroxy organic substance whose hydroxy group reacts with phosphorus pentasulfide. In one approach, the starting alcohol is a substituted aryl hydroxy compound such as a saturated alcohol or an aryl hydroxy compound substituted by a saturated alkyl group. In some approaches, the organic hydroxy compound is one or more of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, tert-butyl alcohol, sec-butyl alcohol, phenol, naphthol, amyl alcohol, hexyl alcohol, iso-hexyl alcohol, octyl alcohol, decyl alcohol, dodecyl alcohol, octadecyl alcohol, 2-ethylhexyl alcohol, 4-methyl-2-pentyl alcohol, phenyl alcohol, butylphenyl alcohol, cyclohexyl alcohol, methylcyclopentyl alcohol, propenyl alcohol, butenyl alcohol, or a combination thereof, C 1 ~C 10 (In other approaches, C 1 ~C 6 ) may be a straight-chain or branched alcohol, a hydroxyaryl compound, or a mixture thereof. Preferred organic hydroxy compounds herein include C 1 ~C 4 alcohols such as ethyl alcohol, propyl alcohol, or isopropyl alcohol, and most preferably, the organic hydroxy compound is isobutyl alcohol.

[0061] Suitable unsaturated carboxylic acids for forming the oil-soluble phosphorus antiwear additive of the present disclosure can include a wide variety of unsaturated carboxylic acids or fatty acids. Preferred unsaturated carboxylic acids include C 1 ~C 20Unsaturated fatty acids can be mentioned, and most preferably it is methacrylic acid. (As used herein, (meth)acrylic acid refers to either acrylic acid or methacrylic acid.)

[0062] In some embodiments, the second phosphorus-providing additive is an acidic thiophosphate or thiophosphate ester present in the additive concentrate in an amount that provides 800 ppm to 1300 ppm of phosphorus and less than 2800 ppm of sulfur to the additive concentrate. In another embodiment, the second phosphorus-providing additive is an acidic thiophosphate or thiophosphate ester present in the additive concentrate in an amount that provides 900 ppm to 1200 ppm of phosphorus and less than 2500 ppm of sulfur to the additive concentrate. In one approach, the additive concentrate contains from about 80 wt% to about 1.75 wt% of an ashless dialkyldithiophosphate compound, and in other approaches, it contains from about 0.9 wt% to about 1.40 wt%, from about 1.0 wt% to about 1.3 wt%.

[0063] In some methods or embodiments, the electric motor lubricating fluid herein may also contain a second phosphorus-providing additive in the form of an ashless dialkyldithiophosphate compound in an amount that provides from about 40 to about 70 ppm of phosphorus and less than 160 ppm of sulfur to the fluid. In some embodiments, the electric motor lubricating fluid herein may contain a second phosphorus-providing additive in the form of an ashless dialkyldithiophosphate compound in an amount that provides from about 50 to about 65 ppm of total phosphorus and less than 140 ppm of sulfur to the fluid. In one method or embodiment, the electric motor lubricating fluid herein contains from about 0.03 wt% to about 0.1 wt% of an ashless dialkyldithiophosphate compound, and in other methods, it contains from about 0.04 wt% to about 0.08 wt%.

[0064] Sulfur-providing additive: The electric motor lubricating fluid contains a sulfur-providing additive. In the methods or embodiments of this specification, the sulfur-providing additive may be one or more thiadiazole compounds or hydrocarbyl-substituted derivatives thereof that provide sulfur to the lubricating fluid of this specification but in an amount that provides sulfur of 950 ppm or less. In other methods, the sulfur-providing compound may be a mixture of thiadiazole compounds or hydrocarbyl-substituted derivatives thereof. Examples of thiadiazole compounds that can be used include, but are not limited to, 2,5-dimercapto-1,3,4-thiadiazole, 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazole, 2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazole, 2,5-bis(hydrocarbylthio)-1,3,4-thiadiazole, or 2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazole. 1,3,4-Thiadiazole is generally synthesized from hydrazine and carbon disulfide by known methods. See, for example, U.S. Patent No. 2,765,289, U.S. Patent No. 2,749,311, U.S. Patent No. 2,760,933, U.S. Patent No. 2,850,453, U.S. Patent No. 2,910,439, U.S. Patent No. 3,663,561, U.S. Patent No. 3,862,798, and U.S. Patent No. 3,840,549.

[0065] In the method, the thiadiazole or its derivative contains one or more compounds having the structure of Formula III,

[0066]

Chemical formula

[0067]

Chemical formula

[0068]

Chemical formula

[0069] The thiadiazole compound or its hydrocarbyl-substituted derivative is present in the electric motor lubricating fluid herein in an amount that delivers about 950 ppm or less sulfur, about 925 ppm or less sulfur, or about 900 ppm or less sulfur, and in other embodiments, at least about 700 ppm sulfur, or at least about 800 ppm sulfur (or other ranges therein). In one embodiment, the thiadiazole compound is 2,5-dimercapto-1,3,4-thiadiazole, and this thiadiazole compound or its hydrocarbyl-substituted derivative is present in the lubricating and cooling fluid in an amount that delivers about 700 to about 950 ppm sulfur, or about 750 to about 900 ppm sulfur (or other ranges therein).

[0070] Base oil: The electric motor lubricating fluid herein includes one or more base oils having a lubricating viscosity. Suitable base oils for use in formulating an electric motor lubricating fluid for use in an electric vehicle and / or hybrid vehicle according to the present disclosure can be selected from any of suitable synthetic or natural oils or mixtures thereof having a suitable lubricating viscosity. Natural oils may include animal oils, and vegetable oils (e.g., castor oil, lard oil), and mineral oils such as liquid petroleum and paraffin-based, naphthenic-based, or solvent-treated or acid-treated mineral lubricating oils of the mixed paraffin-naphthenic type. Oils derived from coal or shale may also be suitable. Further, oils derived from the gas liquefaction process may also be suitable. The base oil can have a kinematic viscosity at 100 °C of about 2 to about 15 cSt as measured by ASTM D2270-10.

[0071] The base oil used in the present invention described herein can be a single base oil or a mixture of two or more base oils. The one or more base oils can be selected from any of Group III or IV base oils specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. Such base oil groups are shown in Table 1 below.

[0072]

Table 1

[0073] In one variant form, the base oil can be selected from API Group III base oils, or API Group IV base oils, or a mixture of these base oils. Alternatively, the base oil can be a mixture of two or more of API Group III base oils, or two or more of API Group IV base oils.

[0074] API Group III base oils can include oils derived from Fischer-Tropsch synthetic hydrocarbons. Fischer-Tropsch synthetic hydrocarbons are produced from synthesis gas containing H 2 and CO using a Fischer-Tropsch catalyst. Such hydrocarbons typically require further processing to be useful as base oils. These types of oils are generally referred to as gas-to-liquid oils (GTL). For example, the hydrocarbons can be hydroisomerized using the processes disclosed in U.S. Patent No. 6,103,099 or 6,180,575, or hydrocracked or hydroisomerized using the processes disclosed in U.S. Patent No. 4,943,672 or 6,096,940, or dewaxed using the method disclosed in U.S. Patent No. 5,882,505, or hydroisomerized and dewaxed using the processes disclosed in U.S. Patent No. 6,013,171, 6,080,301, or 6,165,949.

[0075] PAO, which is an API Group IV base oil, is typically derived from monomers having 4 to 30, or 4 to 20, or 6 to 16 carbon atoms. Examples of PAO that can be used in the present invention include those derived from octene, decene, mixtures thereof, and the like. PAO can have a kinematic viscosity of 2 to 15, or 3 to 12, or 4 to 8 cSt at 100 °C as measured by ASTM D2270-10. Examples of PAO include PAO having a kinematic viscosity of 4 cSt at 100 °C, PAO having a kinematic viscosity of 6 cSt at 100 °C, and mixtures thereof.

[0076] The base oil, in combination with an additive composition as disclosed in the embodiments of this specification, provides a lubricating and cooling fluid for use within an electric motor system having an electric motor, gears, and a clutch. Thus, the base oil can be present in the lubricating and cooling fluid in an amount greater than about 80 wt% based on the total weight of the lubricating and cooling fluid. In some embodiments, the base oil can be present in the lubricating and cooling fluid in an amount greater than about 85 wt% based on the total weight of the lubricating and cooling fluid.

[0077] Other additives The electric motor lubricating fluid described herein can also include conventional additives of the type used in transmission fluid compositions in addition to the components described above. Such additives include, but are not limited to, antioxidants, viscosity modifiers, phosphorus-containing components, detergents, corrosion inhibitors, rust inhibitors, defoamers, demulsifiers, pour point depressants, seal swell agents, and additional dispersants, additional friction modifiers, and additional sulfur-containing components.

[0078] Antioxidants: In some embodiments, the electric motor lubricating fluid contains one or more antioxidants. Suitable antioxidants include, among others, phenolic antioxidants, aromatic amine antioxidants, sulfur-containing antioxidants, and organic phosphites.

[0079] Examples of phenolic antioxidants include 2,6-di-tert-butylphenol, a liquid mixture of tributylated phenols, 2,6-di-tert-butyl-4-methylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), and 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 cycloalkylated diphenylamine. Examples include sterically hindered tertiary butylated phenols, bisphenols, and cinnamic acid derivatives, and combinations thereof.

[0080] Examples of aromatic amine antioxidants include the following formula:

[0081] [Chemical formula] (wherein R' and R'' each independently represent a substituted or unsubstituted aryl group having 6 to 30 carbon atoms), and diarylamines having the same are included, but are not limited thereto. Examples of substituents of the aryl group include aliphatic hydrocarbon groups such as alkyl having 1 to 30 carbon atoms, hydroxy groups, halogen radicals, carboxylic acid or ester groups, or nitro groups.

[0082] The aryl group is preferably substituted or unsubstituted phenyl or naphthyl, and in particular, one or both of the aryl groups are substituted with at least one alkyl having 4 to 30 carbon atoms, preferably 4 to 18 carbon atoms, and most preferably 4 to 9 carbon atoms. It is preferred that one or both of the aryl groups are substituted, for example, a monoalkylated diphenylamine, a di-alkylated diphenylamine, or a mixture of mono- and di-alkylated diphenylamines.

[0083] Examples of diarylamines that can be used include diphenylamine; various alkylated diphenylamines, 3-hydroxydiphenylamine, N-phenyl-1,2-phenylenediamine, N-phenyl-1,4-phenylenediamine, monobutyldiphenyl-amine, dibutyldiphenylamine, monooctyldiphenylamine, dioctyldiphenylamine, monononyldiphenylamine, dinonyldiphenylamine, monotetradecyldiphenylamine, ditetradecyldiphenylamine, phenyl-alpha-naphthylamine, monooctylphenyl-alpha-naphthylamine, phenyl-beta-naphthylamine, monoheptyldiphenylamine, diheptyldiphenylamine, p-oriented styrenated diphenylamine, mixed butyloctyldiphenylamine, and mixed octylstyryldiphenylamine, but are not limited thereto.

[0084] Examples of 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 olefins that can be used include alpha-olefins, isomerized alpha-olefins, branched olefins, cyclic olefins, and combinations thereof.

[0085] Examples of alpha-olefins include, but are not limited to, any C 4 ~C 25 alpha-olefins. Alpha-olefins can be isomerized before or during the sulfurization reaction. Structural isomers and / or conformational isomers of alpha-olefins containing internal double bonds and / or branches can also be used. For example, isobutylene is the branched olefin counterpart of the alpha-olefin 1-butene.

[0086] Sulfur sources that can be used in the vulcanization reaction of olefins include elemental sulfur, sulfur monochloride, sulfur dichloride, sodium sulfide, sodium polysulfide, and mixtures of these added together at different stages of the vulcanization process.

[0087] Unsaturated oils can also be vulcanized due to their unsaturation and can also be used as antioxidants. Examples of oils or fats that can be used include corn oil, canola oil, cottonseed oil, grape seed oil, olive oil, palm oil, peanut oil, coconut oil, rapeseed oil, safflower seed oil, sesame seed oil, soybean oil, sunflower seed oil, tallow, and combinations thereof.

[0088] The total amount of antioxidant in the lubricating and cooling fluids herein can be present in an amount that delivers up to about 200 ppm of nitrogen, or up to about 150 ppm of nitrogen, or about 100 to about 150 ppm of nitrogen.

[0089] Friction modifiers: In some embodiments, the electric motor lubricating fluid contains additional friction modifiers other than those contained within the friction modifier systems described above. Suitable additional friction modifiers can include metal-containing and metal-free friction modifiers, and suitable friction modifiers include, but are not limited to, imidazoline, amide, amine, succinimide, alkoxylated amine, alkoxylated ether amine, amine oxide, amide amine, nitrile, betaine, quaternary amine, imine, amine salt, aminoguanidine, alkanolamide, phosphonate, metal-containing compounds, glycerol esters, sulfurized fatty compounds and olefins, sunflower oil, other naturally occurring vegetable or animal oils, dicarboxylic acid esters, esters or partial esters of polyols, and one or more aliphatic or aromatic carboxylic acids, etc.

[0090] Suitable friction modifiers can contain a hydrocarbyl group selected from linear, branched, or aromatic hydrocarbyl groups, or mixtures thereof, and such hydrocarbyl groups can be saturated or unsaturated. The hydrocarbyl group can be composed of carbon and hydrogen or heteroatoms such as sulfur or oxygen. The hydrocarbyl group can range from 12 to 25 carbon atoms. In some embodiments, the friction modifier can be a long-chain fatty acid ester. In another embodiment, the long-chain fatty acid ester can be a mono-ester, or a di-ester, or a (tri)glyceride. The friction modifier can be a long-chain fatty amide, a long-chain fatty ester, a long-chain fatty epoxide derivative, or a long-chain imidazoline.

[0091] Other suitable friction modifiers can include organic, ashless (metal-free), nitrogen-free organic friction modifiers. Such friction modifiers include esters formed by reacting carboxylic acids and anhydrides with alkanols and can generally include polar end groups (such as carboxyl or hydroxyl) covalently bonded to a lipophilic hydrocarbon chain. Examples of organic ashless nitrogen-free friction modifiers are generally known as glycerol monooleate (GMO) which can contain mono-, di-, and tri-esters of oleic acid. Other suitable friction modifiers are described in U.S. Patent No. 6,723,685.

[0092] Amine-based friction modifiers can include amines or polyamines. Such compounds can have a hydrocarbyl group that is either saturated or unsaturated, linear, or mixtures thereof, and can contain from 12 to 25 carbon atoms. Further examples of suitable friction modifiers include alkoxylated amines and alkoxylated ether amines. Such compounds can be linear and can have a hydrocarbyl group that is either saturated or unsaturated, or mixtures thereof. They can contain from about 12 to about 25 carbon atoms. Examples include ethoxylated amines and ethoxylated ether amines.

[0093] 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. Patent No. 6,300,291.

[0094] If the additional friction modifier contains nitrogen, such additional friction modifier may be present in the lubricating and cooling fluid in any amount as long as the performance requirements are not impaired.

[0095] Detergents: The metal detergents that can be included in the electric motor lubricating fluids described herein generally include a polar head and a long hydrophobic tail, and the polar head consists 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 (measured by ASTM D2896) of 0 to less than 150. A large amount of metal base can be included by reacting an excess metal compound such as an oxide or hydroxide with an acidic gas such as carbon dioxide. The resulting overbased detergent contains micelles of the neutralized detergent surrounding a core of an inorganic metal base (e.g., hydrated carbonate). Such overbased detergents may have a TBN of about 150 or more, for example, about 150 to about 450 or more.

[0096] Detergents that may be suitable for use in the present embodiment include oil-soluble overbased, low-based, and neutral sulfonates, phenates, sulfurized phenates, and salts of metals, particularly alkali or alkaline earth metals such as sodium, potassium, lithium, calcium, and magnesium salicylates. More than one metal, such as both calcium and magnesium, may be present. A mixture of calcium and / or magnesium and 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. Mixtures of such salts may also be used.

[0097] Metal-containing detergents may be present in the lubricating and cooling fluid in an amount sufficient to improve the rust prevention performance of the fluid. The metal-containing detergent may be present in the fluid in an amount sufficient to provide up to 90 ppm of alkali and / or alkaline earth metal based on the total weight of the lubricating and cooling fluid. In one example, the metal-containing detergent may be present in an amount sufficient to provide from about 20 to about 50 ppm of alkali and / or alkaline earth metal. In another embodiment, the metal-containing detergent may be present in an amount sufficient to provide from about 30 to about 40 ppm of alkali and / or alkaline earth metal.

[0098] In one approach, the preferred detergent may be a neutral to low basicity sulfonate, and in some approaches, it may be calcium sulfonate. Suitable detergents have a TBN of 50 or less (e.g., about 25 to about 30) and may be calcium sulfonates that provide about 50 ppm or less of calcium to the lubricant. In other approaches, the detergent can provide about 25 to about 40 ppm of calcium, about 30 to about 40 ppm of calcium, or about 30 to about 38 ppm of calcium to the finished electric motor lubricating fluid or composition. With respect to the additive concentrate, the detergent can provide more than about 950 ppm of calcium relative to the additive concentrate, or about 500 to about 950 ppm of calcium, about 550 to about 900 ppm of calcium, about 600 to about 800 ppm of calcium, or about 600 to about 700 ppm of calcium relative to the additive concentrate.

[0099] Corrosion inhibitors: Rust preventives or corrosion inhibitors may also be included in the electric motor lubricating fluids described herein. Such materials include monocarboxylic acids and polycarboxylic acids. Examples of suitable monocarboxylic acids are octanoic acid, decanoic acid, and dodecanoic acid. Suitable polycarboxylic acids include dimer and trimer acids formed from acids such as tall oil fatty acid, oleic acid, and linoleic acid.

[0100] Another useful type of rust inhibitor can be alkenyl succinic acids and alkenyl succinic anhydride corrosion inhibitors such as, for example, tetrapropenyl succinic acid, tetrapropenyl succinic anhydride, tetradecenyl succinic acid, tetradecenyl succinic anhydride, hexadecenyl succinic acid, hexadecenyl succinic anhydride. Half esters of alkenyl succinic acids having 8 to 24 carbon atoms in the alkenyl group with alcohols such as polyglycol are also useful. Other suitable rust inhibitors or corrosion preventives include ether amines, acidic phosphates, amines, ethoxylated amines, ethoxylated phenols, polyethoxylated compounds such as ethoxylated alcohols, imidazolines, aminosuccinic acid or its derivatives, and the like. Mixtures of such rust inhibitors or corrosion inhibitors can be used. The total amount of corrosion preventive present in the lubricating composition described herein can range from up to 2.0 wt% or 0.01 to 1.0 wt% based on the total weight of the lubricating composition.

[0101] Viscosity modifier: The electric motor lubricating fluid can optionally contain one or more viscosity modifiers. Suitable viscosity modifiers can 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 alkenyl aryl conjugated diene copolymers, or mixtures thereof. The viscosity modifier may include star polymers, and suitable examples are described in U.S. Patent Application Publication No. 2012 / 0101017 (A1).

[0102] The electric motor lubricating fluid described herein may also optionally contain one or more dispersant viscosity modifiers in addition to, or in place of, the viscosity modifier. Suitable dispersant viscosity modifiers can include functionalized polyolefins, such as ethylene-propylene copolymers functionalized with the reaction product of an acylating agent (such as maleic anhydride) and an amine, polymethacrylates functionalized with an amine, or esterified maleic anhydride-styrene copolymers reacted with an amine.

[0103] The total amount of viscosity modifier and / or dispersant viscosity modifier, if present, can be up to about 1.0 wt%, or up to about 0.5 wt%, or up to about 0.3 wt% based on the total weight of the lubricating and cooling fluid.

[0104] Demulsifier: Demulsifiers can include trialkyl phosphates, as well as various polymers and copolymers of ethylene glycol, ethylene oxide, propylene oxide, including polyethylene oxide, polypropylene oxide, and (ethylene oxide-propylene oxide) polymers, or mixtures thereof. If present, the amount of demulsifier in the lubricating and cooling fluid can be up to about 0.05 wt, or up to about 0.02 wt%, or less than about 0.015 wt% based on the total weight of the lubricating and cooling fluid.

[0105] Antifoaming agent: Antifoaming agents used to reduce or prevent the formation of stable foam can include silicones, polyacrylates, or organic polymers. Antifoaming agents that may be useful in the compositions of the disclosed invention can include polysiloxanes, copolymers of ethyl acrylate and 2-ethylhexyl acrylate, and optionally vinyl acetate. If present, the amount of antifoaming agent in the lubricating and cooling fluid can be up to about 0.1 wt, or up to about 0.05 wt%, or less than about 0.04 wt% based on the total weight of the lubricating and cooling fluid.

[0106] Pour point depressant: The electric motor lubricating fluid may optionally contain one or more pour point depressants. Suitable pour point depressants may include esters of maleic anhydride-styrene, polymethacrylate, polymethyl methacrylate, polyacrylate or polyacrylamide, or mixtures thereof. When a pour point depressant is present, it may be present in an amount of about 0.001 wt% to about 0.04 wt% based on the total weight of the lubricant.

[0107] Generally, the lubricating and cooling fluids described herein may include additive components within the ranges listed in Table 2.

[0108] [Table 2]

[0109] The percentages of the above components represent the weight percentages of each component based on the total weight of the lubricating and cooling fluid containing the listed components. The additives used in formulating the compositions described herein may be blended into the base oil individually or in various partial combinations. However, it may be preferred to use an additive concentrate (i.e., an additive plus a diluent such as a hydrocarbon solvent) to blend all of the components simultaneously. 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. Also, the use of a concentrate shortens the mixing time and reduces the possibility of mixing errors.

[0110] As described above, additive concentrates containing a relatively high molecular weight succinimide dispersant, an amine salt of a phosphate ester, an ashless dialkyldithiophosphate, and a thiadiazole or its derivative had viscosities at kV100°C that were much higher than those commonly used in vehicle lubricants having viscosities of about 4.5 cSt or less, about 3.5 cSt or less, or about 3.0 cSt or less. In some approaches, the additive concentrates herein of such components have a kV100°C of about 15 to about 80 cSt, but when used in a finished fluid having the recited elemental relationships, the electric motor lubricating fluids herein still have a finished kV100°C of about 4.5 cSt or less, about 3.5 cSt or less, or about 3.0 cSt or less, along with improved wear, conductivity, and oxidation stability. In some embodiments, the ratio of the kV100°C of the additive concentrate to the kV100°C of the finished fluid is about 5:1 to about 30:1. Any embodiment of the electric motor lubricating fluids herein shows only a slight viscosity change after aging, such as a change of about 0.10 cSt or less (e.g., 0.01 to 0.1 cSt or 0.04 to 0.08 cSt) after the fluid has been aged at 170°C to 180°C for at least 192 hours according to CEC L-48-A. The electric motor lubricating fluids herein also achieve at least 8 destruction load stages in the FZG A10 / 16.6R / 90 scuffing test of CEC L-84-02. Finally, the electric motor lubricating fluids herein also have an electrical conductivity of about 60 nS / M or less (e.g., about 20 to about 60 nS / M) as measured by a modified conductivity test in accordance with ASTM D2624-15 using the electric motor lubricating fluid and measured at 20 Hz and about 100°C using a full-con epsilon tester or equivalent. It was surprising that such low-viscosity fluids having low conductivity and high oxidation stability were able to achieve the above-acceptable performance in the FZG A10 / 16.6R / 90 scuffing test of CEC L-84-02.

Examples

[0111] A better understanding of the present disclosure and many of its advantages can be obtained with reference to the following examples. The following examples are illustrative only and are not intended to limit it in any way as to scope or spirit. Those skilled in the art will readily appreciate that various modifications of the components, methods, steps, and devices described in these examples can be used. Unless otherwise specified, or unless it is clear from the context of the discussion throughout the following examples and the present disclosure, all percentages, ratios, and parts described in the present disclosure are by weight.

[0112] To demonstrate how high molecular weight dispersants can be used in low viscosity fluids to achieve acceptable wear and conductivity, the systems herein compared fluids having various elemental relationships of nitrogen, boron, sulfur, and / or phosphorus, and evaluated the wear, oxidation stability, and conductivity of the fluids in extremely low viscosity fluids having a kinematic viscosity at 100 °C of about 4.5 cSt or less, about 3.5 cSt or less, about 3.0 cSt or less, or about 2.9 cSt or less. The formulations were evaluated for FZG scuffing, oxidation viscosity stability, and electrical conductivity.

[0113] FZG scuffing was used to evaluate the scuffing load capacity of the lubricant and was performed according to the A10 / 16.6R / 90 test of CEC L-84-02. The results are reported at the failure load stage, and better results are obtained for samples having a higher failure load stage.

[0114] Oxidation viscosity stability was used to evaluate the difference between the initial viscosity and the final viscosity after aging the fluid for 192 hours at operating conditions of 170 °C to 180 °C in accordance with CEC L-48-A-00. Aging was performed at 170 °C for the fluids of this example. Lower values suggest improved performance. Thus, fluids with high oxidation stability show only minor viscosity changes measured before and after aging.

[0115] It is beneficial for the electric motor fluid to exhibit low conductivity. The conductivity of the fluid was measured at 1.5 V, 20 Hz, and 100 °C using a full-con Epsilon+ in accordance with a modified version of ASTM D2624-15 (testing lubricants instead of fuels).

[0116] All of the formulations of the present invention and comparative formulations tested in Table 3 below contained various amounts of sulfur components, phosphorus additives, detergents, and dispersants, as shown in Table 3. Each fluid further contained the same antioxidant, antifoaming agent, and process oil. The antioxidant and antifoaming agent were added to each fluid at the same treatment rate. The formulations of the present invention and comparative formulations were tested in the same base oil to obtain finished fluids having the kinematic viscosities at 100 °C shown in the table below. The formulations of the present invention contain additives similar to the comparative formulations, but the delivery of sulfur, phosphorus, and dispersants was balanced differently to achieve surprisingly improved wear, oxidation stability, and lubricant conductivity. The details of these components are described below: · Sulfur component (S-1): 2,5-dimercapto-1,3,4-thiadiazole and / or its derivatives containing approximately 35 wt% sulfur, a 75:25 to 85:15 mixture of 2,5-bis-(nonyldithio)-1,3,4-thiadiazole and 2,5-mono-(nonyldithio)-1,3,4-thiadiazole. · Dispersant (Disp-1): A phosphorylated and borylated succinimide dispersant made from a mixture of polyisobutylene of 950 Mn, maleic anhydride, polyalkylene polyamine having an average of 6.5 nitrogen atoms per molecule, phosphoric acid, and boric acid. This dispersant contained approximately 0.76 wt% phosphorus, approximately 0.35 wt% boron, and approximately 1.75% nitrogen. · Dispersant 2 (Disp-2): A phosphorylated and borylated succinimide dispersant made from a mixture of polyisobutylene of 2100 Mn, maleic anhydride, polyalkylene polyamine having an average of 6.5 nitrogen atoms per molecule, phosphoric acid, and boric acid. The dispersant had approximately 0.77 wt% nitrogen, approximately 0.15 wt% boron, and approximately 0.35 wt% phosphorus. · Phosphorus Additive 1 (P-1): An amine salt of a phosphate ester containing a mixture of dihexyl phosphate and monohexyl phosphate and a di- and / or tri-alkylated amine having an alkyl group of C 12 ~C 14 This phosphorus source contained about 2.5 wt% nitrogen and about 4.9 wt% phosphorus. · Phosphorus Additive 2 (P-2): An ashless dialkyldithiophosphate containing at least 3-[[bis(2-methylpropoxy)phosphinothioyl]thio]-2-methyl-propanoic acid · Detergent Additive 1 (Det-1): Calcium neutral sulfonate having a TBN of about 25 to about 30 and about 2.6 wt% calcium.

[0117] All fluids tested herein contained the same blend of Group III and Group IV base oils. As shown in the table below, all examples of the present invention delivered too little or too much phosphorus and showed improved wear performance, conductivity performance, and oxidation stability compared to comparative examples containing relatively low molecular weight dispersant additives. All fluids were considered low viscosity fluids having a kinematic viscosity at 100 °C (ASTM D445) of about 4.5 cSt or less.

[0118]

Table 3

[0119]

Table 4

[0120]

Table 5

[0121] The lubricating compositions of the present disclosure are described along with their detailed description and the summary herein. However, the foregoing description is intended to illustrate, and not limit, the scope of the present disclosure as defined by the appended claims. Other aspects, advantages, and modifications are within the scope of the claims. The specification and examples are considered illustrative only, and the true scope of the present disclosure is intended to be indicated by the following claims.

[0122] 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" may refer to one or more than one. Unless otherwise indicated, all numbers expressing quantities of ingredients, molecular weights, percentages, ratios, reaction conditions, and the like, used in the specification are to be understood as being modified in all instances by the term "about," whether or not the term "about" is present. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification 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 a broad scope of 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 resulting from the standard deviation found in their respective testing measurements.

[0123] It should be understood that each component, compound, substituent, or parameter disclosed herein is disclosed for use alone or in combination with one or more of any other component, compound, substituent, or parameter disclosed herein.

[0124] It should be 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, the range of 1 to 4 should be construed as a distinct disclosure of the values of 1, 2, 3, and 4, as well as any range of values such as 1 to 4, 1 to 3, 1 to 2, 2 to 4, 2 to 3, etc.

[0125] It should be further understood that each lower limit of each range disclosed herein should be construed 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 construed 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.

[0126] Furthermore, a specific amount / value of a component, compound, substituent, or parameter disclosed in the description or examples should be construed as a disclosure of either the lower or upper limit of a range, and thus can form a range for that component, compound, substituent, or parameter in combination with any other lower or upper limit or specific amount / value of a range for the same component, compound, substituent, or parameter disclosed elsewhere in the present application.

Claims

1. 1. An electric motor lubricating fluid suitable for electric or hybrid electric vehicles, comprising: one or more base oils of lubricating viscosity; a succinimide dispersant derived from polyisobutylene having a number average molecular weight of about 2,000 or greater, having about 0.5 to about 1 weight percent nitrogen, and post-treated with a phosphorus-containing compound and a boron-containing compound to deliver about 70 to about 140 ppm phosphorus and about 150 to about 300 ppm nitrogen to said electric motor lubricating fluid; an amine salt of a phosphoric acid ester providing about 40 to 70 ppm phosphorus to said electric motor lubricating fluid; an oil soluble phosphorus antiwear additive comprising an ashless dialkyldithiophosphate providing from about 40 to about 70 ppm phosphorus to said electric motor lubricating fluid; a sulfur-providing additive comprising a thiadiazole or derivative thereof providing up to 950 ppm sulfur to said electric motor lubricating fluid; An electric motor lubricating fluid having a kV100°C of about 4.5 cSt or less and about 150 to about 250 ppm total phosphorus.

2. The amine salt of a phosphate ester has the structure of Formula I, or a solvate or hydrate thereof: 【Chemistry 1】 During the ceremony, R １ and R ２ are independently 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 ３ , R ４ , R ５ and R ６ are independently hydrogen or a hydrocarbyl group; R ３ ~R ６ At least one of R is a hydrocarbyl group, preferably １ and R ２ is independently ３ ~C １０ is an alkyl group, R ３ , R ４ , R ５ and R ６ At least one of １０ ~C ２０ 10. The electric motor lubricating fluid of claim 1, wherein the alkyl group is an alkyl group.

3. 10. The electric motor lubricating fluid of claim 1, wherein the high molecular weight polyisobutylene has a number average molecular weight of about 2,000 to about 2,300, and / or the electric motor lubricating fluid comprises about 2 to about 4 weight percent of the succinimide dispersant.

4. the succinimide dispersant, the amine salt of a phosphoric acid ester, the ashless dialkyldithiophosphate, and 10. The electric motor lubricating fluid of claim 1, wherein the thiadiazole or derivative thereof is provided in an additive concentrate, said additive concentrate having a kV100°C of from about 15 to about 80 cSt, and / or the ratio of kV100°C of said additive concentrate to kV100°C of said electric motor lubricating fluid is from about 5:1 to about 30:

1.

5. 10. The electric motor lubricating fluid of claim 1, wherein the electric motor lubricating fluid has a viscosity change of less than 0.09 cSt after the electric motor lubricating fluid is aged according to CEC L-48-A), and / or the electric motor lubricating fluid achieves a failure load stage of at least 8 in the FZG A10 / 16.6R / 90 Scuffing Test of CEC L-84-02, and / or the electric motor lubricating fluid has an electrical conductivity of about 60 nS / M or less, measured by a Modified Conductivity Test according to ASTM D2624-15 using the electric motor lubricating fluid, measured at 20 Hz and 100° C.

6. The oil soluble phosphorus anti-wear additive comprising the ashless dialkyl dithiophosphate is made by a process comprising: (a) reacting an organic hydroxy compound with phosphorus pentasulfide to form a reaction product; and further reacting the reaction product with an unsaturated carboxylic acid to form the oil soluble phosphorus anti-wear additive comprising the ashless dialkyl dithiophosphate; and / or the ashless dialkyl dithiophosphate comprises a compound of Formula II or a salt thereof: 【Chemistry 2】 R ７ and R ８ is independently ３ ~C ８ is a linear or branched alkyl group; R ９ is -H or -CH ３ and preferably said ashless dialkyldithiophosphate is 3-[[bis(2-methylpropoxy)phosphinothioyl]thio]-2-methyl-propanoic acid.

7. The thiadiazole or derivative thereof includes one or more compounds having the structure of Formula III: 【Chemistry 3】 During the ceremony, Each R １０ are independently hydrogen or sulfur; Each R １１ are independently an alkyl group; n is an integer of 0 or 1; R １０ is hydrogen, the adjacent R １１ The integer n in the moiety is 0, and R １０ is sulfur, the adjacent R １１ the integer n of the moiety is 1, At least one R １０ 10. The electric motor lubricating fluid of claim 1, wherein:

8. 10. The electric motor lubricating fluid of claim 1, further comprising one or more metal-containing detergent additives providing about 50 ppm or less of calcium to said electric motor lubricating fluid.

9. 1. An additive concentrate suitable for electric motor lubricating fluids comprising: a succinimide dispersant derived from a high molecular weight polyisobutylene having a number average molecular weight of about 2,000 or greater, having about 0.5 to about 1 weight percent nitrogen, and post-treated with a phosphorus-containing compound and a boron-containing compound, present in an amount to deliver about 1400 to about 2450 ppm phosphorus and about 3000 to about 5400 ppm nitrogen to said dispersant additive concentrate; an amine salt of a phosphoric acid ester providing about 1000 to 1500 ppm phosphorus to said additive concentrate; an oil soluble phosphorus antiwear additive comprising an ashless dialkyldithiophosphate providing from about 800 ppm to about 1300 ppm phosphorus to said additive concentrate; a sulfur-providing additive comprising a thiadiazole or derivative thereof providing sulfur to the additive concentrate, the sulfur-providing additive providing no more than about 18,000 ppm sulfur; The additive concentrate has a kV100°C of about 15 cSt to about 80 cSt.

10. 10. The additive concentrate of claim 9, wherein said number average molecular weight of said high molecular weight polyisobutylene is from about 2,000 to about 2,300, and / or said succinimide dispersant comprises from about 40 to about 70 weight percent of said additive concentrate, and / or further comprises one or more metal-containing detergent additives providing up to about 950 ppm calcium to said additive concentrate.

11. 1. A method for lubricating a driveline component including an electric motor, comprising: lubricating the driveline components with an electric motor lubricating composition, the electric motor lubricating composition contacting parts of the electric motor; The electric motor lubricating composition comprises: (i) one or more base oils of lubricating viscosity; (ii) a succinimide dispersant derived from a high molecular weight polyisobutylene having a number average molecular weight of greater than or equal to about 2,000, having about 0.5 to about 1 weight percent nitrogen, and post-treated with a phosphorus-containing compound and a boron-containing compound to deliver about 70 to about 140 ppm phosphorus and about 150 to about 300 ppm nitrogen to the electric motor lubricating fluid; (iii) an amine salt of a phosphoric acid ester providing about 40 to 70 ppm phosphorus to the electric motor lubricating fluid; (iv) an oil soluble phosphorus antiwear additive comprising an ashless dialkyldithiophosphate providing about 40 to about 70 ppm phosphorus to the electric motor lubricating fluid; and (v) a sulfur providing additive comprising a thiadiazole or derivative thereof providing sulfur to the electric motor lubricating fluid, but not exceeding about 950 ppm sulfur.

1. A method for lubricating driveline components including an electric motor, wherein the electric motor lubricating fluid has a kV100°C of about 3.5 cSt or less, a total phosphorus of about 150 to about 200 ppm, and an electrical conductivity of about 37 nS / M or less, measured by a modified conductivity test in accordance with ASTM D2624-15, measured at 20 Hz and 100°C, using the electric motor lubricating fluid.

12. 12. The method for lubricating driveline components including electric motors as recited in claim 11, wherein the number average molecular weight of the high molecular weight polyisobutylene is from about 2,000 to about 2,300, and / or the electric motor lubricating fluid comprises from about 2 to about 4 weight percent of the succinimide dispersant.

13. 12. The method for lubricating a driveline component including an electric motor as recited in claim 11, wherein the succinimide dispersant, the amine salt of a phosphoric acid ester, the oil soluble phosphorus antiwear additive comprising an ashless dialkyldithiophosphate, and the sulfur providing additive comprising a thiadiazole or derivative thereof are provided in an additive concentrate having a kV100°C of about 15 to about 80 cSt, and / or the electric motor lubricating composition further comprises one or more metal-containing detergent additives providing no more than about 50 ppm calcium to the electric motor lubricating composition.

14. 14. The method for lubricating a driveline component including an electric motor as recited in claim 13, wherein the ratio of kV 100°C of said additive concentrate to kV 100°C of said electric motor lubricating fluid is from about 5:1 to about 30:

1.

15. 12. The method for lubricating a driveline component including an electric motor as recited in claim 11, wherein the electric motor lubricating fluid has a viscosity change of less than 0.09 cSt after the electric motor lubricating fluid is aged according to CEC L-48-A and / or the electric motor lubricating fluid achieves a failure load stage of at least 8 in the FZG A10 / 16.6R / 90 scuffing test of CEC L-84-02.

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