Lubrication fluid for electric motor system

Abstract

To provide an electric motor driving system fluid that offers acceptable wear performance as well as good electric conductivity and oxidation stability for use in an electric motor system fluid with low viscosity when selected elemental relationships of phosphorus, sulfur, and calcium are included in the fluid.SOLUTION: An electric motor driving system fluid for an electric motor system comprises a lubricant base oil, at least one sulfurized component, and at least one dispersant derived from polyisobutylene having a number-average molecular weight of at least 2000.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 a drive system 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 and / or drive system of an electric or hybrid electric vehicle, comprising an oil of lubricating viscosity and at least one high molecular weight dispersant.

Background Art

[0002] A major challenge in developing lubricants for the drive systems of electric vehicles is to achieve acceptable friction performance and maintain oxidation stability while ensuring lubricant compatibility with the charged components in the drive system. Lubricants within electric 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 the charged components.

[0003] To improve efficiency, lubricant manufacturers often try to reduce the viscosity of the lubricant, but lower viscosity fluids are often not very desirable for the severe wear tests often required by industry and / or automotive manufacturers. Thus, lower viscosity fluids 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 / or decreases the oxidation stability or viscosity stability.

[0004] In particular, in order to improve shutter durability, it is common to include one or more friction modifiers in conventional transmission lubricants. However, lubricants for the drive systems of electric vehicles tend to be adversely affected by high levels of friction modifiers, and friction modifiers can interfere with the performance of other components in the lubricant, such as anti-wear additives. Therefore, in the case of low-viscosity lubricants configured for use in electric or hybrid electric vehicles, it can be difficult to achieve the desired performance in terms of wear resistance, oxidation stability, conductivity, corrosion, and / or friction performance. SUMMARY OF THE INVENTION

[0005] In one approach or embodiment, an electric drive system fluid suitable for an electric or hybrid electric vehicle is described herein. In one aspect of this approach or embodiment, the electric drive system fluid comprises one or more base oils of lubricating viscosity and a succinimide dispersant derived from polyisobutylene having a number average molecular weight of about 2000 or greater, the succinimide dispersant having a maximum of about 1 weight percent nitrogen, post-treated with a phosphorus-containing compound and a boron-containing compound, delivering about 150 to about 270 ppm of dispersant phosphorus (P) to the electric drive system fluid, a sulfur-providing additive comprising a thiadiazole or a derivative thereof, the thiadiazole or its derivative providing at least about 1000 ppm of thiadiazole sulfur (S) to the electric drive system fluid, a combination of dispersant phosphorus and thiadiazole sulfur (P+S) being at least about 1300 ppm, a weight ratio of dispersant phosphorus to thiadiazole sulfur (P / S) being at least about 0.1, a detergent system providing one or more calcium-containing detergents, the one or more calcium-containing detergents providing about 200 ppm or less of calcium, and containing a friction modifier of about 0.4 weight percent or less, the electric drive system fluid having a kV100 viscosity of about 3.2 cSt or greater, a total phosphorus of about 150 to about 270 ppm, and an electrical conductivity of about 130 nS / M or less as measured by a modified conductivity test in accordance with ASTM D2624-15 and measured at 20 Hz and 170 °C.

[0006] In other methods or embodiments, the electrically driven system fluid described in the previous paragraph may include one or more optional features or embodiments in any combination. These optional features or embodiments can include one or more of the following: the friction modifier is an alkyl imide, alkyl amine, hydrocarbyl imidazole, their derivatives, or combinations thereof, and / or the friction modifier includes 0 to about 0.4 weight percent of one or more linear or branched C16 - C18 substituted succinic acids or anhydrides reacted with an amine, polyamine, or ammonia (preferably reacted with ammonia), 0 to about 0.08 weight percent of ethoxylated alkyl amine (preferably ethoxylated tallow amine), and / or the friction modifier is 0 to about 0.1 weight percent of linear or branched C16 - C18 substituted succinic acids or anhydrides reacted with an amine, polyamine, or ammonia (preferably reacted with ammonia), and / or the number average molecular weight of the polyisobutylene is from about 2000 to about 2400, and / or the electric motor lubricating fluid includes from about 2 to about 8 weight percent (preferably from about 4 to about 8 weight percent) of a succinimide dispersant, and / or the electrically driven system fluid has a viscosity change of less than about 0.5 cSt after aging according to CEC L - 48 - A, and / or the electrically driven system fluid achieves at least about 8 failure load stages in the FZG A10 / 16.6R / 120 scuffing test of CEC L - 84 - 02, and / or the thiadiazole or its derivative provides sulfur at about 1500 ppm or less, and / or the combination of dispersant phosphorus and thiadiazole sulfur (P + S) is from about 1300 ppm to about 1400 ppm, and / or the weight ratio of dispersant phosphorus to thiadiazole sulfur (P / S) is from about 0.1 to about 0.3, and / or about 90 to about 100% of the total phosphorus is provided by the succinimide dispersant, and / or the amount of phosphorus provided is about 1 ppm of phosphorus per 8 - 13 number average molecular weight units of the polyisobutylene portion of the succinimide dispersant, and / or the thiadiazole or its derivative includes one or more compounds having the structure of formula I.

[0007] [Chem.] Each R in formula III 10 is, independently, hydrogen or sulfur, and each R in formula III 11 is, independently, an alkyl group, n is an integer of 0 or 1, and when R 10 is hydrogen, the integer n of the adjacent R 11 portion is 0, and when R 10 is sulfur, n of the adjacent R 11 portion is 1, and at least one R 10 is sulfur.

[0008] In another approach or embodiment, a method for lubricating drive train components including an electric motor is described herein. In aspects of this embodiment, the method includes lubricating the drive train components with an electric drive train fluid, and in some embodiments, the electric drive train fluid contacts portions of the electric motor. In other aspects of this embodiment, the electric drive train fluid is (i) one or more base oils of lubricating viscosity, and (ii) a succinimide dispersant derived from polyisobutylene having a number average molecular weight of about 2000 or greater, the succinimide dispersant having up to about 1 weight percent nitrogen, post-treated with a phosphorus-containing compound and a boron-containing compound, delivering about 150 to about 270 ppm of dispersant phosphorus (P) to the electric drive train fluid, a succinimide dispersant, and (iii) a sulfur-providing additive including a thiadiazole or a derivative thereof providing at least about 1000 ppm (preferably about 1000 to about 1400 ppm) of thiadiazole sulfur (S) to the electric drive train fluid, wherein the combination of dispersant phosphorus and thiadiazole sulfur (P + S) is at least about 1300 ppm (preferably about 1300 to about 1400), and the weight ratio of dispersant phosphorus to thiadiazole sulfur (P / S) is at least about 0.1 (preferably about 0.1 to about 0.3), a sulfur-providing additive, and (iv) a detergent system providing one or more calcium-containing detergents, the one or more calcium-containing detergents providing up to about 200 ppm of calcium, a detergent system, and (v) a friction modifier of about 0.4 weight percent or less, the electric drive train fluid having a kV100 viscosity of about 3.2 cSt or greater, a total phosphorus of about 150 to about 270 ppm, and an electrical conductivity of about 130 nS / M or less as measured by a modified conductivity test conducted in accordance with ASTM D2624-15 and measured at 20 Hz and 170 °C.

[0009] In a further method or embodiment, the method for lubricating the drive train components including the electric motor as described in the previous paragraph can 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, where the friction modifier is an alkyl imide, alkyl amine, hydrocarbyl imidazole, their derivatives, or a combination thereof, and / or the friction modifier is 0 to about 0.08 weight percent ethoxylated alkyl amine (preferably ethoxylated tallow amine), and / or the organic friction modifier is 0 to about 0.4 weight percent linear or branched C16 - C18 substituted succinic acid or anhydride reacted with an amine, polyamine, or ammonia (preferably reacted with ammonia), and / or the number average molecular weight of the polyisobutylene is about 2000 to about 2400, and / or the electric drive train fluid contains about 2 to about 8 weight percent succinimide dispersant (preferably about 4 to about 8 weight percent), and / or the electric drive train fluid has a viscosity change of less than about 0.5 cSt after aging the electric drive train fluid according to CEC L - 48 - A, and / or the electric drive train fluid achieves at least about 8 failed load stages in the FZG A10 / 16.6R / 120 scuffing test of CEC L - 84 - 02, and / or about 90 to about 100 percent of the total phosphorus is provided by the succinimide dispersant, and / or the thiadiazole or its derivative contains one or more compounds having the structure of Formula III,

[0010] [Chemical formula] Each R 10 is independently hydrogen or sulfur, each R 11 is independently an alkyl group, n is an integer of 0 or 1, and when R 10 is hydrogen, the integer n of the adjacent R 11 portion is 0, and when R 10 is sulfur, the n of the adjacent R 11 portion is 1, and at least one R 10 is sulfur.

[0011] In other methods or embodiments, the use of the electric drive system fluid described herein is such that it achieves one or more of: (i) an electrical conductivity of about 130 nS / M or less, measured by a modified conductivity test in accordance with ASTM D2624-15 and measured at 20 Hz and 170 °C using the electric drive system fluid; (ii) a viscosity change of less than about 0.5 cSt after the electric drive system fluid has been aged in accordance with CEC L-48-A; and / or (iii) at least about 8 failure load stages in the FZG A10 / 16.6R / 120 scuffing test of CEC L-84-02. In such embodiments, the electric drive system fluid includes any of the embodiments described in this summary and comprises at least (i) one or more base oils of lubricating viscosity, and (ii) a succinimide dispersant derived from polyisobutylene having a number average molecular weight of about 2000 or greater, wherein the succinimide dispersant has a maximum of about 1 weight percent nitrogen, is post-treated with a phosphorus-containing compound and a boron-containing compound, and delivers about 150 to about 270 ppm of dispersant phosphorus (P) to the electric drive system fluid; (iii) a sulfur-providing additive comprising a thiadiazole or a derivative thereof that provides at least about 1000 ppm (preferably about 1000 to about 1400 ppm) of thiadiazole sulfur (S) to the electric drive system fluid, wherein the combination of dispersant phosphorus and thiadiazole sulfur (P+S) is at least about 1300 ppm (preferably about 1300 to about 1400), and the weight ratio of dispersant phosphorus to thiadiazole sulfur (P / S) is at least about 0.1 (preferably about 0.1 to about 0.3); (iv) a detergent system that provides one or more calcium-containing detergents, wherein the one or more calcium-containing detergents provide about 200 ppm or less of calcium; and (v) a friction modifier of about 0.4 weight percent or less, and the electric drive system fluid has a kV100 viscosity of about 3.2 cSt or greater and a total phosphorus of about 150 to about 270 ppm.

[0012] Other embodiments of the disclosure will be apparent to those skilled in the art in view of the specification and practice of the invention disclosed herein.

[0013] The following definitions of terms are provided to clarify the meaning of specific terms used in this specification.

[0014] The terms "lubricating oil", "lubricant composition", "lubricating composition", "lubricant", and "lubricating and cooling fluid" refer to a finished lubricating product that contains a major amount of base oil and a minor amount of additive composition.

[0015] 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.

[0016] 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 having a carbon atom directly bonded to the remainder of the molecule and having predominantly hydrocarbon character. Each hydrocarbyl group is independently selected from hydrocarbon substituents, and a substituted hydrocarbon substituent contains one or more of a halo group, a hydroxyl group, an alkoxy group, a mercapto group, a nitro group, a nitroso group, an amino group, a pyridyl group, a furyl group, an imidazolyl group, oxygen, and nitrogen, and two or fewer non-hydrocarbon substituents are present per ten carbon atoms in the hydrocarbyl group.

[0017] 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.

[0018] As used herein, the terms "soluble", "oil-soluble", or "dispersible" 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 such an extent that they exhibit their intended effects, for example, in an environment where oil is used. Further, if desired, the incorporation of other additives may also enable the incorporation of higher levels of specific additives.

[0019] As used herein, the term "alkyl" refers to straight-chain, branched-chain, cyclic, and / or substituted saturated chain moieties of from about 1 to about 200 carbon atoms.

[0020] As used herein, the term "alkenyl" refers to straight-chain, branched-chain, cyclic, and / or substituted saturated chain moieties of from about 3 to about 30 carbon atoms.

[0021] As used herein, the term "aryl" refers to monocyclic and polycyclic aromatic compounds containing alkyl, alkenyl, alkylaryl, amino, hydroxyl, alkoxy, halo substituents, and / or heteroatoms, such as, but not limited to, nitrogen and oxygen.

[0022] 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).

[0023] Throughout this disclosure, terms such as "comprises," "includes," "contains," etc. are considered to be open-ended and should be understood to include any element, step, or ingredient not explicitly recited. The phrase "consisting essentially of" means including any explicitly recited 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 recited components.

Mode for Carrying Out the Invention

[0024] According to an exemplary embodiment, a low-viscosity drive system lubricant suitable for electric or hybrid electric vehicles having a selected elemental relationship is described herein that achieves surprisingly qualified performance in demanding FZG scuffing tests such as the A10 / 16.6R / 90 test of CEC L-84-02, while at the same time achieving good electrical conductivity and maintaining oxidation stability. However, what is surprising about the lubricating fluids herein is that a particular combination of additives including a succinimide dispersant derived from polyisobutylene having a number average molecular weight greater than 2000 has been found to be useful for achieving qualified wear, conductivity, and oxidation performance when such a dispersant is used in combination with a selected elemental relationship of phosphorus, sulfur, and calcium. In some embodiments, it has also been discovered that certain friction modifiers need to be limited in the composition.

[0025] When the selected succinimide dispersant of the present specification is combined with other lubricant additives having specific elemental relationships (e.g., the relationships of phosphorus, sulfur, and / or calcium further considered below) to form a finished lubricant, the finished lubricant of the present specification achieves lower viscosity, acceptable scuffing performance, suitable conductivity, and / or oxidation stability, and makes the fluid suitable for the drive system of electric or hybrid electric vehicles.

[0026] The fluid of the present specification comprises at least (i) a succinimide dispersant derived from polyisobutylene having a number average molecular weight of at least about 2000 or more, having a maximum of about 1 weight percent nitrogen, post-treated with a phosphorus-containing compound and a boron-containing compound, and delivering about 150 to about 270 ppm of dispersant phosphorus (P) to the electric drive system fluid, and (ii) a sulfur-providing additive comprising a thiadiazole or a derivative thereof, wherein the thiadiazole or a derivative thereof provides at least about 1000 ppm of sulfur (S) to the electric drive system fluid. Further, in order to achieve the performance of an electric or hybrid electric vehicle, it has been found that the total amount (P+S) of phosphorus delivered from the dispersant phosphorus and sulfur delivered from the thiadiazole or a derivative thereof needs to be at least about 1300 ppm (preferably, about 1300 ppm to about 2000 ppm, about 1300 ppm to about 1600 ppm, or about 1300 ppm to about 1400 ppm), and the weight ratio (P / S) of phosphorus delivered from the dispersant phosphorus and sulfur delivered from the thiadiazole or a derivative thereof needs to be at least about 0.1 (preferably, about 0.1 to about 0.5, about 0.1 to about 0.4, or about 0.1 to about 0.3).

[0027] Furthermore, other embodiments of the lubricants herein also include a selected detergent system and / or a selected friction modifier system to achieve suitable performance for hybrid and / or hybrid electric vehicles. In one embodiment, the lubricants herein further include a detergent system that provides one or more calcium-containing detergents but has only a limited amount of calcium. Preferably, the detergent system includes one or more calcium-containing detergents that provide calcium at about 200 ppm or less. In still other embodiments, the lubricants herein can further include a selected friction modifier system having a friction modifier of about 0.4 weight percent or less, including alkylamides, alkylimides, alkylamines, hydrocarbylamines, hydrocarbyl polyamines, hydrocarbylimidazoles, their derivatives, or combinations thereof. As further described below, the lubricants herein may include only a limited amount of ethoxylated alkylamine friction modifier and / or a limited amount of alkylated succinic acid or its anhydride or derivative. For example, the lubricants herein may include a friction modifier that includes less than 0.1 weight percent of ethoxylated alkylamine (preferably ethoxylated tallow amine), and / or less than 0.3 weight percent of alkylated succinic acid or its anhydride or derivative.

[0028] When the electric drive system fluid of this specification has a relatively low kinematic viscosity of about 3.2 cSt or more (preferably about 3.2 cSt to about 7 cSt), and a total phosphorus of about 150 to about 270 ppm in combination with the other components, relationships, and systems described above, the lubricant simultaneously exhibits low electrical conductivity, acceptable anti-wear performance, and / or desired oxidation stability. For example, the fluid of this specification is measured by a modified conductivity test in accordance with ASTM D2624-15 using the following (i) electric drive system fluid, and has an electrical conductivity of about 130 nS / M or less when measured at 20 Hz and 170 °C, (ii) a viscosity change of less than about 0.5 cSt after the electric drive system fluid is aged in accordance with CEC L-48-A, and / or (iii) at least about 8 failure load stages in the FZG A10 / 16.6R / 120 scuffing test of CEC L-84-02. Each of the component additives, relationships, and systems is further described below.

[0029] Succinimide dispersant The electric motor drive system fluid of this specification contains a dispersant system having at least one oil-soluble ashless dispersant, which is preferably a succinimide dispersant derived from 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. The succinimide dispersant of this specification can be derived from a hydrocarbyl-substituted dicarboxylic acid or anhydride reacted with a polyalkylene polyamine. The succinimide dispersants and their preparations 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.

[0030] The hydrocarbyl portion 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 conventional polyisobutylene or highly reactive polyisobutylene having a terminal vinylidene content of at least about 60%, such as about 70% to about 90% or more. Suitable polyisobutylenes can include those prepared using a BF3 catalyst.

[0031] The number average molecular weight of the polyisobutylene substituent of the dispersant in this specification may vary from at least about 2000 and sometimes up to about 3000 when determined by gel permeation chromatography (GPC) using polystyrene (number average molecular weight 180 to about 18,000) as the calibration standard. The GPC method further provides weight average 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.

[0032] The polyisobutylene moiety in the dispersant of this specification also has 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, and in other methods, a suitable polyisobutylene substituent has a polydispersity of about 1.5 to about 3.0, or about 2.0 to about 3.0.

[0033] Dicarboxylic acids or anhydrides suitable for forming the dispersants of this specification can be selected from carboxylic acid-based reactants including 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 anhydride, ethyl maleic acid, dimethyl maleic acid, hexyl maleic acid, etc., corresponding acid halides and C1-C4 aliphatic esters. In some procedures, the molar ratio of the dicarboxylic acid or anhydride to the hydrocarbyl portion 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, a particularly suitable molar ratio of the acid or anhydride to the hydrocarbyl portion is from 1:1 to less than 1.6:1. In other embodiments, another useful charge molar ratio of the dicarboxylic acid or anhydride to the hydrocarbyl portion may be from 1:1 to 1.5:1, or from 1:1 to 1.4:1, or from 1.1:1 to 1.3:1, or from 1:1 to 1.2:1.

[0034] Any of a number of polyalkylene polyamines can be used in the preparation of the dispersant additives of the present 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 seven or more nitrogen atoms and two or more primary amines per molecule, and include mixtures of polyalkylene polyamines with 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 may be from about 1:1 to about 3.0:1. In one embodiment, the dispersant in the present disclosure described herein may be a reaction product of polyisobutenyl succinic anhydride (PIBSA) and a polyamine, such as a heavy polyamine, and the charge molar ratio of the polyisobutenyl-substituted succinic anhydride to the polyamine is from about 1.7:1 to about 2.5:1.

[0035] As described above, the succinimide dispersant of the present specification may be post-treated with a boron compound. Suitable boron compounds useful for forming the dispersant in the present specification include any boron compound or mixture of boron compounds capable of introducing 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 boronic acid such as boric acid (e.g., alkyl-B(OH)2, or aryl-B(OH)2), boric acid (i.e., H3BO3), tetraboric acid (i.e., H2B5O7), 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 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.

[0036] The succinimide dispersant of this specification 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 the ashless dispersant. For this reason, any organic or inorganic phosphorus compound capable of undergoing such a reaction can be used. Therefore, 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, etc. For this reason, such compounds can be used, for example, as phosphorous acid (sometimes represented as H3PO3, H2(HPO3), and sometimes called ortho-phosphorous acid or phosphoric acid), phosphoric acid (sometimes called orthophosphoric acid H3PO4), hypophosphoric acid (H4P2O6), metaphosphoric acid (HPO3), pyrophosphoric acid (H4P2O7), hypophosphorous acid (sometimes called phosphinic acid H3PO2), pyrophosphorous acid (sometimes called pyrophosphonic acid H4P2O5), phosphinous acid (H3PO), tripolyphosphoric acid (H5P3O10), tetrapolyphosphoric acid (H5P4O13), trimeta-phosphoric acid (H3P3O9), phosphorus trioxide, phosphorus tetroxide, phosphorus pentoxide, etc.Partial or all sulfur analogs such as phosphorotetrathioic acid (H3PS4), phosphoromonothioic acid (H3PO3S), phosphorodithioic acid (H3PO2S2), phosphorotrithioic acid (H3POS3), sesquisulfide phosphorus, heptasulfide phosphorus, and phosphorus pentasulfide (sometimes referred to as P2S5, P4S10) can also be used to form the dispersant for the present disclosure. Inorganic phosphorus halide compounds such as PCl3, PBr3, POCl3, and PSCl3 can also be used.

[0037] Similarly, organic phosphorus compounds such as 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" R2P(O)(OR)), esters of phosphinic acid, phosphonyl halides (e.g., RP(O)Cl2 and R2P(O)Cl), halophosphates (e.g., (RO)PCl2 and (RO)2PCl), halophosphites (e.g., ROP(O)Cl2 and (RO)2P(O)Cl), tertiary pyrophosphate esters (e.g., (RO)2P(O)-O-P(O)(OR)2), and total sulfur analogs or partial sulfur analogs of any of the aforementioned organic phosphorus compounds 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., tetrahalohydrocarbyl phosphorus, trihalodihydrocarbyl phosphorus, and dihalotrihydrocarbyl phosphorus), and halophosphines (monohalophosphines and dihalophosphines) can also be used.

[0038] In one embodiment, the fluid succinimide dispersant of the present specification includes at least a polyisobutenyl moiety having a number average molecular weight of at least about 2000, in another approach 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, includes a polyisobutenyl moiety having a number average molecular weight of at least 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.

[0039] In some embodiments, the dispersants described herein include about 2 to about 8 weight percent (preferably about 4 to about 8 weight percent) of an electric motor drive train fluid and deliver about 300 to about 600 ppm nitrogen, about 150 to about 270 ppm phosphorus, and about 50 to about 120 ppm boron to the finished fluid. 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 acceptable wear and conductivity performance, as well as oxidation stability, suitable for lubricants used in the drive train or powertrain of electric and / or hybrid electric vehicles.

[0040] Sulfur-providing additive The electric motor drive fluid also contains a sulfur-providing additive in an amount that improves wear performance, conductivity, and oxidation stability when combined with the succinimide described above. In the methods or embodiments herein, the sulfur-providing additive provides at least about 1000 ppm sulfur (preferably about 1000 to about 1500 ppm sulfur, more preferably about 1000 to about 1400 ppm sulfur, most preferably about 1000 to about 1300 ppm sulfur) to the lubricating fluid herein, and may be one or more thiadiazole compounds or hydrocarbyl-substituted derivatives thereof. 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 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 some embodiments, the form and amount of the sulfur-providing additive herein contribute to the ability of the fluid to maintain low conductivity and oxidation stability while also meeting other desired wear performance characteristics. In the method, the thiadiazole or its derivative includes one or more compounds having the structure of Formula III,

[0042]

Chemical Formula

[0043] [Chemical formula] In formula IIIa, each integer n is 1, each R1 is sulfur, and each R2 is a C5-C15 alkyl group, preferably a C8-C12 alkyl group,

[0044] [Chemical formula] In formula IIIb, one integer n is 1, the related R2 group is a C5-C15 alkyl group (preferably a C8-C12 alkyl group), the other integer n is 0, and both R1s are sulfur. In some embodiments, the sulfur-providing additive comprises a blend of formula IIIa and IIIb, with formula Iva being the majority of the blend. In other methods, the blend of IIIa and IIIb is about 75 to about 90 weight percent of IIIa and about 10 to about 25 weight percent of IIIb (or other ranges therein). In another method, the sulfur-providing additive is 2,5-dimercapto-1,3,4-thiadiazole comprising a blend of 2,5-bis-(nonyldithio)-1,3,4-thiadiazole (such as about 75 to about 90%) and 2,5-mono-(nonyldithio)-1,3,4-thiadiazole (such as about 10 to about 25%).

[0045] The thiadiazole compound or a hydrocarbyl-substituted derivative thereof is present in the electric motor lubricating fluid herein in an amount that delivers at least about 1000 ppm sulfur, at least about 1100 ppm sulfur, or at least about 1200 ppm sulfur. In embodiments, the thiadiazole compound or a hydrocarbyl-substituted derivative thereof is present in the electric motor lubricating fluid herein in an amount that delivers from about 1000 to about 1500 ppm sulfur, in other embodiments from about 1000 to about 1400 ppm sulfur, or from about 1000 to about 1300 ppm sulfur. In one embodiment, the thiadiazole compound is 2,5-dimercapto-1,3,4-thiadiazole, and this thiadiazole compound or a hydrocarbyl-substituted derivative thereof is present in the lubricating fluid in an amount that delivers from about 1000 to about 1300 ppm (or other ranges within that range) sulfur.

[0046] Friction modifier In some embodiments, the electric motor drive system fluid herein contains only low levels of friction modifier, particularly, contains less than about 0.4 weight percent of friction modifier. As used herein, the electric motor drive system fluid contains less than about 0.4 weight percent of a friction modifier that includes an alkylamide, an alkylimide (having one or more C15-C30 alkyl chains), an alkylamine, a hydrocarbylamine, a hydrocarbylpolyamine, a hydrocarbylimidazole, derivatives thereof, or combinations thereof. In one embodiment, the electric drive system fluid herein may have a friction modifier, but may have from about 0.3 weight percent or less of a linear or branched C16-C18 substituted succinic acid or anhydride reacted with ammonia. In another embodiment, the electric drive system fluid herein may contain from about 0.3 weight percent or less of a linear or branched C16-C18 substituted succinic acid or anhydride reacted with an amine, polyamine, or ammonia, and / or from 0 to about 0.05 weight percent of an alkyl- or alkenyl-substituted imidazoline, and / or from 0 to about 0.08 weight percent of an ethoxylated alkylamine (preferably ethoxylated tallow amine).

[0047] In other embodiments, the electric drive train fluids herein may have a friction modifier including a linear or branched C16 - C18 substituted succinic acid or anhydride friction modifier or derivatives thereof obtained by reaction with an amine, polyamine, or ammonia (preferably ammonia) of about 0.10 weight percent or less, and / or an alkyl or alkenyl substituted imidazoline of less than about 0.05 weight percent. In other embodiments, the electric drive train fluids herein may have a friction modifier of about 0.30 weight percent or less, including a linear or branched C16 - C18 substituted succinic acid or anhydride friction modifier or derivatives thereof obtained by reaction with an amine, polyamine, or ammonia and / or an ethoxylated tallow alkylamine of less than about 0.08 weight percent.

[0048] In other embodiments, the limited amount of friction modifier in the lubricants herein may also include a small amount of any metal - containing and / or a small amount of organic or metal - free friction modifiers, and may include only a small amount of such friction modifiers including imidazolines, amides, amines, succinimides, alkoxylated amines, alkoxylated ether amines, amine oxides, amidoamines, nitriles, betaines, quaternary amines, imines, amine salts, aminoguanidines, alkanolamides, phosphonic acids, metal - containing compounds, glycerol esters, sulfurized aliphatic compounds and olefins, sunflower oil and other naturally occurring vegetable or animal oils, dicarboxylic acid esters, esters or partial esters of polyols with one or more aliphatic or aromatic carboxylic acids, etc.

[0049] Friction modifiers that tend to be limited in the lubricants of this specification can contain a hydrocarbyl group selected from a straight-chain, branched-chain, or aromatic hydrocarbyl group, or a mixture 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.

[0050] Other friction modifiers that tend to be restricted in the lubricants of this specification 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 lipophilic hydrocarbon chains. Examples of organic ashless nitrogen-free friction modifiers are generally known as glyceryl 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.

[0051] Amine friction modifiers may also be limited in the lubricants of this specification, and such friction modifiers may include amines or polyamines. Such compounds can have hydrocarbyl groups that are either straight-chain saturated or unsaturated, or mixtures thereof, and may 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 saturated, unsaturated hydrocarbyl groups, or mixtures thereof. They can contain from about 12 to about 25 carbon atoms. Examples include ethoxylated amines and ethoxylated ether amines. 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.

[0052] In any embodiment of this specification, the lubricants of this specification, if present, contain up to about 0.4 weight percent total friction modifiers, particularly up to about 0.4 weight percent of the friction modifiers of the above types. In some embodiments, the lubricants of this specification are substantially free of, or preferably do not contain, friction modifiers, which means that the lubricant has up to about 0.4 weight percent of such friction modifiers, up to about 0.2 weight percent of friction modifiers, up to about 0.1 weight percent of friction modifiers, up to about 0.08 weight percent of friction modifiers, up to about 0.06 weight percent of friction modifiers, up to about 0.04 weight percent of friction modifiers, up to about 0.02 weight percent of friction modifiers, up to about 0.01 weight percent of friction modifiers, or no measurable amount of the above friction modifiers.

[0053] Base oil The electric motor drive system fluid of this specification 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 and / or hybrid electric motor vehicle according to the present disclosure can be selected from any of suitable synthetic or natural oils having a suitable lubricating viscosity or mixtures thereof. 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 a gas liquefaction process may also be suitable. The base oil may have a kinematic viscosity of about 2 to about 6 cSt at 100 °C as measured by ASTM D445.

[0054] 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 the 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.

[0055]

Table 1

[0056] In one variant form, the base oil can be selected from API Group III base oils, or API Group IV base oils, or mixtures of these base oils. Alternatively, the base oil can be a mixture of two or more of the API Group III base oils or two or more of the API Group IV base oils.

[0057] API Group III base oils can include oils derived from Fischer-Tropsch synthetic hydrocarbons. 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 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, hydrocracked or hydroisomerized using the processes disclosed in U.S. Patent No. 4,943,672 or 6,096,940, 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.

[0058] 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 with a kinematic viscosity of 4 cSt at 100 °C, PAO with a kinematic viscosity of 6 cSt at 100 °C, and mixtures thereof.

[0059] The base oil is combined with an additive composition as disclosed in the embodiments herein to provide a lubricant for use in an electric motor system having an electric motor, gears, and a clutch. Thus, the base oil can be present in the lubricating fluid in an amount exceeding about 80 weight percent, 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 weight percent, based on the total weight of the lubricating and cooling fluid.

[0060] Other additives The electric motor drive system fluid described in this specification may include, in addition to the components described above, other additives of the types used in electric motor fluid compositions. 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.

[0061] Antioxidant In some embodiments, the electric motor drive system fluid contains one or more antioxidants. Suitable antioxidants include, among others, phenolic antioxidants, aromatic amine antioxidants, sulfurized phenolic antioxidants, and organic phosphite esters.

[0062] Examples of phenolic antioxidants include 2,6-di-tert-butylphenol, a liquid mixture 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), 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.

[0063] Aromatic amine antioxidants include the following formula:

[0064]

Chemical formula

[0065] The aryl group is preferably substituted or unsubstituted phenyl or naphthyl. 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 preferable that one or both of the aryl groups are substituted. For example, it is a monoalkylated diphenylamine, di-alkylated diphenylamine, or a mixture of mono- and di-alkylated diphenylamines.

[0066] Examples of the diarylamine 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 butyloctyl diphenylamine, and mixed octylstyryl diphenylamine, but are not limited to these.

[0067] 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 168-351 g / mol, are preferred. Examples of olefins that can be used include alpha-olefins, isomerized alpha-olefins, branched olefins, cyclic olefins, and combinations thereof.

[0068] Examples of alpha-olefins include, but are not limited to, any C4-C25 alpha-olefin. The alpha-olefin 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.

[0069] Examples of 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 of these added together at different stages of the sulfurization process.

[0070] Unsaturated oils can also be sulfurized due to their unsaturation and can 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, animal fat, and combinations thereof.

[0071] The total amount of antioxidant in the lubricating and cooling fluids described 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 up to about 100 ppm of nitrogen.

[0072] Detergent The metal detergents that can be included in the electric motor drive fluid described in this specification generally include a polar head having 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 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.

[0073] Detergents that may be suitable for use in this embodiment include oil-soluble overbased, low-based, and neutral sulfonates, phenates, sulfurized phenates, and salicylates of metals, particularly alkali or alkaline earth metals such as sodium, potassium, lithium, calcium, and magnesium. More than one metal, such as both calcium and magnesium, may be present. Mixtures of calcium and / or magnesium with sodium may also be suitable. Suitable metal detergents can be overbased calcium or magnesium sulfonates having a TBN of 150 to 450, overbased calcium or magnesium phenates or sulfurized phenates having a TBN of 150 to 300, and overbased calcium or magnesium salicylates having a TBN of 130 to 350. Mixtures of such salts may also be used.

[0074] The metal-containing detergent 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 130 ppm of alkali and / or alkaline earth metal based on the total weight of the lubricating and cooling fluid.

[0075] In one approach, the preferred detergent may be a neutral to low basicity sulfonate, and in some approaches, it may be calcium sulfonate. A suitable detergent may be calcium sulfonate having a TBN of 50 or less (e.g., about 25 to about 30).

[0076] Viscosity modifier The electric motor drive system fluid may optionally contain one or more viscosity modifiers. Suitable viscosity modifiers 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 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).

[0077] The electric motor drive system fluids 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 may 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.

[0078] The total amount of viscosity modifier and / or dispersant viscosity modifier, when present, may 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.

[0079] Antifoaming agent Antifoaming agents used to reduce or prevent the formation of stable foams include silicones, polyacrylates, or organic polymers. Antifoaming agents that may be useful in the disclosed invention's compositions include polysiloxanes, copolymers of ethyl acrylate and 2-ethylhexyl acrylate, and optionally, vinyl acetate. When present, the amount of the 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.

[0080] Pour point depressant The electric motor drive system fluid may optionally contain one or more pour point depressants. Suitable pour point depressants can include esters of maleic anhydride - styrene, polymethacrylates, polymethyl methacrylates, polyacrylates or polyacrylamides, or mixtures thereof. When a pour point depressant is present, it can be present in an amount of about 0.001 wt% to about 0.04 wt% based on the total weight of the lubricant.

[0081] Generally, the lubricating and cooling fluids described herein may include additive components within the ranges listed in Table 2.

[0082]

Table 2

[0083] The percentages of each 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 when formulating the compositions described herein can be blended into the base oil individually or in various partial combinations. However, it may be suitable 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 in the form of the additive concentrate. Also, the use of a concentrate shortens the mixing time and reduces the potential for mixing errors.

Examples

[0084] A better understanding of the present disclosure and many of its advantages can be obtained using the following examples. The following examples are illustrative and in no way limit it in any scope or spirit. Those skilled in the art will readily understand that variations 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.

[0085] To demonstrate how the fluids herein achieve acceptable wear, oxidation stability, and conductivity, the fluids of the present invention herein are compared with fluids having various elemental relationships of nitrogen, boron, sulfur, and / or phosphorus to evaluate wear, oxidation stability, and conductivity. The formulations were evaluated for FZG scuffing, oxidation viscosity stability, and electrical conductivity. As shown in the following table, the examples of the present invention showed improved wear performance, electrical conductivity performance, and oxidation stability compared to the comparative examples. The examples of the present invention having the required components and at the required processing rate were thus suitable for lubricating the drive systems of electric or hybrid electric vehicles. Comparative examples delivering too much phosphorus, too much friction modifier, too much detergent, and / or containing too much dispersant derived from polyisobutylene having too low a number average molecular weight had a decrease in wear performance, a decrease in oxidation stability, and / or a decrease in conductivity and were thus not suitable for lubricating the drive systems of electric or hybrid electric vehicles. All fluids tested herein were considered low-viscosity fluids having a kinematic viscosity at 100 °C (ASTM D445) of about 3.2 to about 8 cSt.

[0086] FZG scuffing is used to evaluate the scuffing load capacity of lubricants and is carried out according to the A10 / 16.6R / 90 test of CEC L-84-02. The results are represented by the failure load stage, and better results are obtained for samples with a higher failure load stage. The lubricants of the present invention herein achieve at least 8 failure load stages.

[0087] Using oxidation viscosity stability, the difference between the initial viscosity and the final viscosity after aging the fluid for 192 hours according to CEC L-48-A-00 was evaluated. Lower values suggest improved performance. Thus, fluids with high oxidation stability show only slight changes in viscosity measured before and after aging. The fluids herein have a viscosity change of about 0.5 cSt or less.

[0088] It is beneficial for an electric motor fluid to exhibit a low conductivity. The conductivity of the fluid was measured at 1.5 V, 20 Hz and 170 °C using Flucon Epsilon+ according to a modified version of ASTM D2624-15 (testing of lubricants, not fuels). The fluids herein have a conductivity of about 130 nS / m or less.

[0089] All of the examples and comparative examples of the present invention tested in Table 3 below contained various amounts of sulfurized components, friction modifiers, and dispersants as shown in Table 3. In other respects, each fluid contained the same additional additives including antioxidants, defoamers, corrosion inhibitors, detergents, demulsifiers, and process oils. The examples and comparative examples of the present invention were tested with Group IV base oils to obtain final fluids having a kinematic viscosity at 100 °C as shown in the following table. The balanced delivery of sulfur, friction modifiers, and phosphorus delivered from the dispersant in the examples of the present invention resulted in surprisingly improved wear, oxidation stability, and lubricant conductivity. Comparative examples that delivered too much phosphorus and / or contained relatively low molecular weight dispersant additives and / or contained too much friction modifier had reduced wear performance, or oxidation stability, and / or lubricant conductivity. The details of these components used in these examples are described below. · Sulfur component (S-1) 2,5-Dimercapto-1,3,4-thiadiazole and / or its derivatives containing approximately 35% by weight of sulfur, which was 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 1 (Disp-1) A phosphorylated and borylated succinimide dispersant made from a mixture of 950Mn polyisobutylene, maleic anhydride, a polyalkylene polyamine having an average of 6.5 nitrogen atoms per molecule, phosphoric acid, and boric acid. This dispersant contained approximately 0.76% by weight of phosphorus, approximately 0.35% by weight of boron, and approximately 1.75% of nitrogen. · Dispersant 2 (Disp-2) A phosphorylated and borylated succinimide dispersant made from a mixture of 2100Mn polyisobutylene, maleic anhydride, a polyalkylene polyamine having an average of 6.5 nitrogen atoms per molecule, phosphoric acid, and boric acid. The dispersant had approximately 0.77% by weight of nitrogen, about 0.15% by weight of boron, and about 0.35% by weight of phosphorus. · Detergent additive 1 (Det-1) Overbased calcium sulfonate having approximately 300 TBN and approximately 11.9 weight percent of calcium · Friction modifier 1 (FM-1) 1-Hydroxy-2-heptadecenyl imidazoline · Friction modifier 2 (FM-2) Branched C16 - C18 substituted succinic acid or anhydride reacted with ammonia. · Friction modifier 3 (FM-3) Ethoxylated tallow alkylamine

[0090] [Table 3] * ASTM D445

[0091] [Table 4]

[0092]

Table 5

[0093] Example 1 of the present invention had acceptable FZG performance (8 or higher), improved oxidation performance (the difference between the initial viscosity and the final viscosity after aging was 0.5 cSt or less), and improved electrical conductivity (130 nS / m or less), while the comparative example had any of reduced FZG performance, reduced oxidation performance, and / or reduced conductive performance.

[0094] Example 2 of the present invention and Comparative Example 5 are shown in Table 6 below. The examples were tested with Group III or Group IV / V base oils to obtain finished fluids having the kinematic viscosities at 100 °C shown in the following table. Example 2 of the present invention and Comparative Example 5 contained various amounts of friction modifiers and detergents, as shown in Table 6 below. In other respects, the examples contained similar amounts of additional additives including antioxidants, antifoaming agents, demulsifiers, and process oils. The balanced delivery of sulfur, friction modifier, and dispersant in Example 2 of the present invention resulted in surprisingly improved wear, oxidation stability, and lubricant conductivity. Comparative Example 5 contained too much friction modifier and too much detergent, and thus had reduced performance in wear, or oxidation stability, and / or lubricant conductivity. Details of the additional components used in these examples are described below. · Dispersant 3 (Disp-3): A succinimide dispersant obtained from a mixture of polyisobutylene of 950 Mn, maleic anhydride, and a polyalkylene polyamine having an average of 6.5 nitrogen atoms per molecule. The dispersant had approximately 2.0 wt% nitrogen. · Friction modifier 4 (FM-4): Linear C16 - C18 substituted succinic acid or anhydride reacted with ammonia. · Friction modifier 5 (FM-5): A mixture of friction modifiers containing isodecyloxypropyl monoamine, n-oleyl-1,3-diaminopropane, and dimethyloctadecylamine · Antioxidant (AO): One or more antioxidants consisting of hindered phenol and alkylated diphenylamine

[0095]

Table 6

[0096]

Table 7

[0097]

Table 8

[0098] Example 2 of the present invention had acceptable FZG performance (8 or more), improved oxidation performance (the difference between the initial viscosity and the final viscosity after aging of 0.5 cSt or less), and improved electrical conductivity (130 nS / m or less), while Comparative Example 5 had decreased FZG performance, decreased oxidation performance, and / or decreased conductivity performance.

[0099] The lubricating compositions of the present disclosure are described along with their detailed description and the summary herein, but it should be understood that the foregoing description is intended to illustrate and not limit the scope of the present disclosure, which is 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.

[0100] 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 the claims, the articles “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. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0101] 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 of the other components, compounds, substituents, or parameters disclosed herein.

[0102] 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.

[0103] 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. Thus, 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.

[0104] 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 driveline fluid comprising: one or more base oils of lubricating viscosity; a succinimide dispersant derived from polyisobutylene having a number average molecular weight of about 2000 or greater, said succinimide dispersant having a maximum of about 1 weight percent nitrogen and being post-treated with a phosphorus-containing compound and a boron-containing compound to deliver about 150 to about 270 ppm of dispersant phosphorus (P) to said electric drive system fluid; a sulfur-providing additive comprising a thiadiazole or a derivative thereof, said thiadiazole or derivative thereof providing at least about 1000 ppm of thiadiazole sulfur (S) to said electric driveline fluid; the combination of said dispersant phosphorus and said thiadiazole sulfur (P+S) is at least about 1300 ppm and the weight ratio of said dispersant phosphorus to said thiadiazole sulfur (P / S) is at least about 0.1; a detergent system providing one or more calcium-containing detergents, said one or more calcium-containing detergents providing about 200 ppm or less of calcium; about 0.4 weight percent or less of a friction modifier; Including, 1. The electric drive system fluid having a kV100 viscosity of about 3.2 cSt or greater, a total phosphorus of about 150 to about 270 ppm, and an electrical conductivity of about 130 nS / M or less measured at 20 Hz and 170° C. using the electric drive system fluid as measured by a modified electrical conductivity test in accordance with ASTM D2624-15.

2. 2. The electric driveline fluid of claim 1, wherein the friction modifier is an alkylimide, an alkylamine, a hydrocarbyl imidazole, derivatives thereof, or combinations thereof, and / or the friction modifier is an ethoxylated alkylamine at 0 to about 0.08 weight percent, and / or the organic friction modifier is an ethoxylated alkylamine at 0 to about 0.4 weight percent of a linear or branched C16-C18 substituted succinic acid or anhydride reacted with an amine, polyamine, or ammonia.

3. 10. The electric driveline fluid of claim 1, wherein the polyisobutylene has a number average molecular weight of about 2000 to about 2400 and / or the electric motor lubrication fluid comprises about 2 to about 8 weight percent of the succinimide dispersant.

4. 10. The electric driveline fluid of claim 1, wherein the electric driveline fluid has a viscosity change of less than 0.5 cSt after aging the electric driveline fluid according to CEC L-48-A.

5. 10. The electric driveline fluid of claim 1, wherein the electric driveline fluid achieves a failing load stage of at least about 8 in the FZG A10 / 16.6R / 120 scuffing test of CEC L-84-02.

6. 10. The electric drivetrain fluid of claim 1, wherein the thiadiazole or derivative thereof provides about 1500 ppm sulfur or less.

7. 2. The electric driveline fluid of claim 1, wherein the combined dispersant phosphorus and thiadiazole sulfur (P+S) is from about 1300 ppm to about 1400 ppm and / or the weight ratio of the dispersant phosphorus to the thiadiazole sulfur (P / S) is from about 0.1 to about 0.

3.

8. 2. The electric drive system fluid of claim 1, wherein about 90 to about 100 percent of the total phosphorus is provided by the succinimide dispersant and / or the amount of phosphorus provided is about 1 ppm phosphorus for every 8 to 13 number average molecular weight units of the polyisobutylene portion of the succinimide dispersant.

9. The thiadiazole or derivative thereof comprises one or more compounds having the structure of Formula I: 【Chemistry 1】 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, then the adjacent R １１ The integer n in the moiety is 0, and R １０ is sulfur, the adjacent R １１ the moiety n is 1, At least one R １０ 2. The electric driveline fluid of claim 1, wherein is sulfur.

10. 1. A method for lubricating a driveline component, including an electric motor, comprising: lubricating the driveline components with an electric driveline fluid; The electric drivetrain fluid comprises (i) one or more base oils of lubricating viscosity; (ii) a succinimide dispersant derived from a polyisobutylene having a number average molecular weight of about 2000 or greater, the succinimide dispersant having a maximum of about 1 weight percent nitrogen and post-treated with a phosphorus-containing compound and a boron-containing compound to deliver about 150 to about 270 ppm of dispersant phosphorus (P) to the electric drivetrain fluid; and (iii) a thiadiazole sulfur (S) providing at least about 1000 ppm to the electric drivetrain fluid. (iv) a detergent system providing one or more calcium-containing detergents, the one or more calcium-containing detergents providing no more than about 200 ppm calcium; and (v) a detergent system providing no more than about 0.4 weight percent of a friction modifier.

13. The method of claim 12, wherein the electrical drive system fluid has a kV100 viscosity of about 3.2 cSt or greater, a total phosphorus of about 150 to about 270 ppm, and an electrical conductivity of about 130 nS / M or less measured at 20 Hz and 170° C. using the electrical drive system fluid as measured by a modified electrical conductivity test in accordance with ASTM D2624-15.

11. 11. The method of lubricating driveline components including electric motors as recited in claim 10, wherein the friction modifier is an alkylimide, an alkylamine, a hydrocarbyl imidazole, derivatives thereof, or combinations thereof, and / or the friction modifier is an ethoxylated alkylamine at 0 to about 0.08 weight percent, and / or the friction modifier is an ethoxylated alkylamine at 0 to about 0.4 weight percent of a linear or branched C16-C18 substituted succinic acid or anhydride reacted with an amine, polyamine, or ammonia.

12. 11. The method of lubricating driveline components including electric motors as recited in claim 10, wherein the polyisobutylene has a number average molecular weight of from about 2000 to about 2400 and / or the electric driveline fluid comprises from about 2 to about 8 weight percent of the succinimide dispersant.

13. 11. The method of lubricating driveline components including electric motors as recited in claim 10, wherein the electric driveline fluid has an aging viscosity change of less than about 0.5 cSt after the electric driveline fluid is aged according to CEC L-48-A.

14. 11. The method of lubricating driveline components including electric motors as recited in claim 10, wherein the electric driveline fluid achieves a failing load stage of at least about 8 in the FZG A10 / 16.6R / 120 scuffing test of CEC L-84-02.

15. about 90 to about 100 percent of the total phosphorus is provided by the succinimide dispersant, and / or the thiadiazole or derivative thereof comprises one or more compounds having the structure of Formula III: 【Chemistry 2】 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, then the adjacent R １１ The integer n in the moiety is 0, and R １０ is sulfur, the adjacent R １１ the moiety n is 1, At least one R １０ 11. The method of lubricating a driveline component including an electric motor as recited in claim 10, wherein: is sulfur.

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