Lubricating Fluids for Electric Motor Systems

Abstract

To provide an electric drive system fluid having acceptable frictional performance, good electric conductivity, and oxidation stability, and a method for lubricating driving system components including an electric motor.SOLUTION: An electric drive system fluid comprises one or more base oils of lubricating viscosity, a succinimide dispersant derived from polyisobutylene having a number-average molecular weight of about 2000 or higher, a sulfur-providing additive including thiadiazole or a derivative thereof, a detergent system providing one or more calcium-containing detergents, and a friction modifier of about 0.4 wt.% or less, wherein the provided electric drive system fluid has a kV100 viscosity of about 3.2 cSt or higher, a total phosphorus content of about 150 to about 270 ppm, and an electric conductivity of about 130 nS / M or less as measured by a modified conductivity test in accordance with ASTM D2624-15 using the electric drive system fluid, measured at 20 Hz and 170°C.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to lubricating fluids for electric motor systems and methods of lubricating drivelines within electric motor systems. In particular, the disclosed methods and lubricating fluids relate to low viscosity lubricating fluids for use in electric motors and / or drivelines of electric or hybrid electric vehicles comprising an oil of lubricating viscosity and at least one high molecular weight dispersant. [Background technology]

[0002] A major challenge in developing a lubricant for an electric vehicle driveline is to ensure lubricant compatibility with charged components in the driveline while achieving acceptable frictional performance and maintaining oxidative stability. Because the lubricant in an electric or hybrid electric vehicle may also come into contact with components in the electric motor, the electrical conductivity of the fluid must also be relatively low to prevent electrostatic build-up and discharge of the charged components.

[0003] To improve efficiency, lubricant manufacturers often attempt to reduce the viscosity of the lubricant, but lower viscosity fluids are often less desirable for the stringent wear tests often required by industrial and / or automotive manufacturers. Thus, lower 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 and / or decreases the oxidation or viscosity stability of the lubricant.

[0004] It is also common to include one or more friction modifiers in conventional transmission lubricants, particularly to improve shudder durability. However, lubricants for electric vehicle drivelines tend to be adversely affected by high levels of friction modifiers, which can interfere with the performance of other components in the lubricant, such as anti-wear additives. Thus, in the context of low viscosity lubricants configured for electric or hybrid electric vehicles, it can be difficult to achieve the desired performance in anti-wear, oxidation stability, electrical conductivity, corrosion, and / or friction performance. Summary of the Invention

[0005] In one approach or embodiment, an electric driveline fluid suitable for electric or hybrid electric vehicles is described herein. In one aspect of this approach or embodiment, the electric driveline fluid comprises one or more base oils of lubricating viscosity; a succinimide dispersant derived from a polyisobutylene having a number average molecular weight of about 2000 or greater, the succinimide dispersant having up to 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 driveline fluid; and a sulfur-providing additive comprising a thiadiazole or derivative thereof, the thiadiazole or derivative thereof delivering at least about 1000 ppm of thiadiazole sulfur (S) to the electric driveline fluid. 1. An electric drive system comprising: a sulfur-providing additive; a detergent system providing to a fluid a combined dispersant phosphorus and thiadiazole sulfur (P+S) of at least about 1300 ppm, a weight ratio of dispersant phosphorus to thiadiazole sulfur (P / S) of at least about 0.1, and one or more calcium-containing detergents, the one or more calcium-containing detergents providing no more than about 200 ppm calcium; and about 0.4 weight percent or less of a friction modifier, the electric drive system having a kV100 viscosity of about 3.2 cSt or greater, about 150 to about 270 ppm total phosphorus, and an electrical conductivity of about 130 nS / M or less when measured at 20 Hz and 170° C. using the electric drive system fluid according to a modified electrical conductivity test in accordance with ASTM D2624-15.

[0006] In other approaches or embodiments, the electric driveline fluids described in the preceding paragraphs may include one or more of the optional features or embodiments in any combination. These optional features or embodiments may include one or more of the following, where the friction modifier is an alkylimide, an alkylamine, a hydrocarbyl imidazole, derivatives thereof, or combinations thereof, and / or the friction modifier is an amine, a polyamine, or 0 to about 0.4 weight percent of one or more linear or branched C16-C18 substituted succinic acids or anhydrides reacted with ammonia (preferably reacted with ammonia), 0 to about 0.08 weight percent of an ethoxylated alkylamine (preferably an ethoxylated alkylamine), and / or the friction modifier is 0 to about 0.1 weight percent of a linear or branched C16-C18 substituted succinic acid or anhydride reacted with an amine, polyamine, or ammonia (preferably reacted with ammonia), and / or the polyisobutylene has a number average molecular weight of from about 2000 to about 2400, and / or the electric motor lubrication fluid comprises from about 2 to about 8 weight percent (preferably from about 4 to about 8 weight percent) of a succinimide dispersant, and / or the electric driveline fluid has a viscosity change of less than about 0.5 cSt after the electric driveline fluid is aged according to CEC L-48-A, and / or the electric driveline fluid has a viscosity change of less than about 0.5 cSt after the electric driveline fluid is aged according to CEC L-84-02 ... and / or the thiadiazole or derivative thereof provides no more than about 1500 ppm of sulfur, and / or the combined 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 from 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 phosphorus for every 8 to 13 number average molecular weight units of the polyisobutylene portion of the succinimide dispersant, and / or the thiadiazole or derivative thereof comprises one or more compounds having the structure of formula I:

[0007] [ka] Each R of formula III 10 is independently hydrogen or sulfur, and each R 11 are independently an alkyl group, n is an integer of 0 or 1, and R 10 If is hydrogen, the adjacent R 11 The integer n in the part is 0, and R 10 If is sulfur, the adjacent R 11 The moiety n is 1 and at least one R 10 is sulfur.

[0008] In another approach or embodiment, described herein is a method for lubricating a driveline component, including an electric motor. In an aspect of this embodiment, the method includes lubricating the driveline component with an electric driveline fluid, and in some embodiments, the electric driveline fluid contacts a portion of the electric motor. In another aspect of this embodiment, the electric driveline 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 driveline fluid; and (iii) a sulfur-providing additive comprising a thiadiazole or derivative thereof providing at least about 1000 ppm (preferably about 1000 to about 1400 ppm) of thiadiazole sulfur (S) to the electric driveline fluid, the dispersant phosphorus .... and a sulfur providing additive having a combined thiadiazole sulfur (P+S) of at least about 1300 ppm (preferably from about 1300 to about 1400) and a weight ratio of dispersant phosphorus to thiadiazole sulfur (P / S) of at least about 0.1 (preferably from about 0.1 to about 0.3); (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) no more than about 0.4 weight percent friction modifier, wherein the electric drive system fluid has a kV100 viscosity of about 3.2 cSt or greater, about 150 to about 270 ppm total phosphorus, and an electrical conductivity of about 130 nS / M or less when measured at 20 Hz and 170° C. using the electric drive system fluid according to a modified electrical conductivity test in accordance with ASTM D2624-15.

[0009] In still further approaches or embodiments, a method for lubricating driveline components including electric motors as described in the preceding paragraph may include one or more optional method steps, features, or embodiments in any combination. These optional method steps, features, or embodiments may include one or more of the following, 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 (preferably an ethoxylated tallow amine) at 0 to about 0.08 weight percent; and / or the organic friction modifier is an amine, a polyamine, or 0 to about 0.4 weight percent of a linear or branched C16-C18 substituted succinic acid or anhydride reacted with ammonia (preferably reacted with ammonia); and / or the polyisobutylene has a number average molecular weight of about 2000 to about 2400; and / or the electric drive system fluid comprises about 2 to about 8 weight percent of a succinimide dispersant (preferably about 4 to about 8 weight percent); and / or the electric drive system fluid comprises a CEC and / or the electric driveline fluid achieves a fail load stage of at least about 8 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 derivative thereof comprises one or more compounds having the structure of Formula III,

[0010] [ka] Each R 10 is independently hydrogen or sulfur; 11 are independently an alkyl group, n is an integer of 0 or 1, and R 10 If is hydrogen, the adjacent R 11 The integer n in the part is 0, and R 10 If is sulfur, the adjacent R 11 The moiety n is 1 and at least one R 10 is sulfur.

[0011] In other approaches or embodiments, the use of the electric driveline fluids described herein are described herein to achieve one or more of: (i) an electrical conductivity of about 130 nS / M or less, measured using the electric driveline fluid at 20 Hz and 170° C. using a Modified Conductivity Test in accordance with ASTM D2624-15; (ii) a viscosity change of less than about 0.5 cSt after the electric driveline fluid is aged in accordance with CEC L-48-A; and / or (iii) a failing load stage of at least about 8 in the FZG A10 / 16.6R / 120 Scuffing Test of CEC L-84-02. In such embodiments, the electric driveline fluid, including any of the embodiments described in this Summary, comprises at least (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 which has been 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 driveline fluid; and (iii) a thiadiazole or derivative thereof that provides at least about 1000 ppm (preferably about 1000 to about 1400 ppm) of thiadiazole sulfur (S) to the electric driveline 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) no more than about 0.4 weight percent friction modifier, wherein the electric drivetrain fluid has a kV100 viscosity of about 3.2 cSt or greater and about 150 to about 270 ppm total phosphorus.

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

[0013] The following definitions are provided to clarify the meaning of certain terms used herein.

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

[0015] As used herein, the terms "additive package," "additive concentrate," and "additive composition" refer to that portion of a lubricating oil composition other than a majority of base oil.

[0016] As used herein, the term "hydrocarbyl substituent" or "hydrocarbyl group" is used in its ordinary sense, which is well known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having a predominantly hydrocarbon character. Each hydrocarbyl group is independently selected from hydrocarbon substituents, the substituted hydrocarbon substituents containing one or more of halo, hydroxyl, alkoxy, mercapto, nitro, nitroso, amino, pyridyl, furyl, imidazolyl, oxygen, and nitrogen, and no more than two non-hydrocarbon substituents are present for every 10 carbon atoms in the hydrocarbyl group.

[0017] As used herein, the term "percent by weight" or "wt%" means the percentage that the recited component represents relative to the weight of the entire composition, unless otherwise specified.

[0018] The terms "soluble", "oil-soluble" or "dispersible" used herein may, but do not necessarily, indicate that a compound or additive is soluble, dissolvable, miscible or suspendable in oil in all proportions. However, the terms mean that they are, for example, soluble, suspendable, soluble or stably dispersible in oil to a sufficient degree to exert their intended effect in the environment in which the oil is used. Furthermore, if desired, the incorporation of other additives may also allow the incorporation of higher levels of the specific additive.

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

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

[0021] As used herein, the term "aryl" refers to mono- 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.

[0022] As used herein, "number average molecular weight" or "Mn" is determined by gel permeation chromatography (GPC) using commercially available polystyrene standards (having Mn of about 180 to about 18,000) as calibration standards.

[0023] Throughout this disclosure, the terms "comprises," "includes," "contains," and the like are considered to be open ended and should be understood to include any element, step, or ingredient not expressly recited. The phrase "consisting essentially of" is meant to include any explicitly recited element, step, or ingredient, as well as any additional elements, steps, or ingredients that do 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 as including a disclosure of the same composition "consisting essentially of" or "consisting of" that specifically recited ingredient. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] According to exemplary embodiments, described herein are low viscosity driveline lubricants suitable for electric or hybrid electric vehicles having selected elemental relationships that surprisingly achieve passing performance in demanding 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, what is surprising about the lubricating fluids herein is that it has been found that certain additive combinations, including succinimide dispersants derived from polyisobutylene having a number average molecular weight greater than 2000, are useful in achieving passing wear, electrical conductivity, and oxidation performance when such dispersants are used in combination with selected phosphorus, sulfur, and calcium elemental relationships. It has also been found that in some embodiments, certain friction modifiers need to be limited in the composition.

[0025] When selected succinimide dispersants herein are combined with other lubricant additives having specific elemental relationships (e.g., phosphorus, sulfur, and / or calcium relationships as discussed further below) to form a finished lubricant, the finished lubricant herein achieves lower viscosity, acceptable scuffing performance, suitable electrical conductivity, and / or oxidation stability, making the fluid suitable for the drivelines of electric or hybrid electric vehicles.

[0026] The fluids herein comprise at least (i) a succinimide dispersant derived from polyisobutylene having a number average molecular weight of about 2000 or greater, having up to about 1 weight percent nitrogen, and post-treated with a phosphorus-containing compound and a boron-containing compound, delivering from 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 derivative thereof, wherein the thiadiazole or derivative thereof provides at least about 1000 ppm of sulfur (S) to the electric drive system fluid. It has further been discovered that to achieve electric or hybrid electric vehicle performance, the combined amount of phosphorus delivered from the dispersant phosphorus and sulfur delivered from the thiadiazole or derivative thereof (P+S) must be at least about 1300 ppm (preferably, from about 1300 ppm to about 2000 ppm, from about 1300 ppm to about 1600 ppm, or from about 1300 ppm to about 1400 ppm), and the weight ratio of phosphorus delivered from the dispersant phosphorus to sulfur delivered from the thiadiazole or derivative thereof (P / S) must be at least about 0.1 (preferably, from about 0.1 to about 0.5, from about 0.1 to about 0.4, or from about 0.1 to about 0.3).

[0027] Further, other embodiments of the lubricants herein also include a selected detergent system and / or a selected friction modifier system to achieve performance suitable 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 limited amounts of calcium. Preferably, the detergent system includes one or more calcium-containing detergents that provide about 200 ppm or less of calcium. In yet other embodiments, the lubricants herein can further include a selected friction modifier system that has about 0.4 weight percent or less of a friction modifier including an alkylamide, an alkylimide, an alkylamine, a hydrocarbylamine, a hydrocarbylpolyamine, a hydrocarbylimidazole, a derivative thereof, or a combination thereof. As further described below, the lubricants herein may include only limited amounts of an ethoxylated alkylamine friction modifier and / or limited amounts of an alkylated succinic acid or anhydride or derivative thereof. For example, the lubricants herein may contain a friction modifier comprising less than 0.1 weight percent of an ethoxylated alkylamine (preferably ethoxylated tallow amine), and / or less than 0.3 weight percent of an alkylated succinic acid or anhydride or derivative thereof.

[0028] When the electric driveline fluids herein have a relatively low kV100 viscosity of about 3.2 cSt or more (preferably about 3.2 cSt to about 7 cSt) and about 150 to about 270 ppm total phosphorus in combination with the other components, relationships, and systems described above, the lubricants simultaneously exhibit low electrical conductivity, acceptable antiwear performance, and / or desirable oxidation stability. For example, the fluids herein exhibit one or more of the following: (i) an electrical conductivity of about 130 nS / M or less when measured by a modified electrical conductivity test in accordance with ASTM D2624-15 using the electric driveline fluid and measured at 20 Hz and 170° C., (ii) a viscosity change of less than about 0.5 cSt after the electric driveline fluid is aged in accordance with CEC L-48-A, and / or (iii) a failing load stage of at least about 8 in the FZG A10 / 16.6R / 120 scuffing test of CEC L-84-02. Each of the component additives, relationships, and systems are further described below.

[0029] Succinimide Dispersants The electric motor drive system fluid herein contains a dispersant system having at least one oil-soluble ashless dispersant, preferably a succinimide dispersant derived from polyisobutylene having a number average molecular weight of about 2000 or more, and post-treated with a phosphorus-containing compound and a boron-containing compound. The succinimide dispersant herein can be derived from a hydrocarbyl-substituted dicarboxylic acid or anhydride reacted with a polyalkylene polyamine. Succinimide dispersants and their preparation are disclosed at least in U.S. Pat. No. 7,897,696 and / or U.S. Pat. No. 4,234,435, which are incorporated herein by reference.

[0030] The hydrocarbyl portion of the hydrocarbyl-dicarboxylic acid or anhydride thereof may be derived from a butene polymer, such as a polymer of isobutylene. Suitable polyisobutylenes for use herein include those formed from conventional polyisobutylene or highly reactive polyisobutylenes having a terminal vinylidene content of at least about 60%, such as from about 70% to about 90% or more. Suitable polyisobutylenes may include those prepared using BF3 catalysts.

[0031] The number average molecular weight of the polyisobutylene substituent of the dispersants herein may vary from at least about 2000 and sometimes up to about 3000 as determined by gel permeation chromatography (GPC) using polystyrene (number average molecular weight 180 to about 18,000) as a calibration standard. The GPC method further provides weight average molecular weight distribution information. See also, for example, W.W. Yau, J.J. Kirkland and D.D. Ly, "Modern Size Exclusion Liquid Chromatography", John Wiley and Sons, New York, 1979, incorporated herein by reference.

[0032] The polyisobutylene moieties in the dispersants herein also 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 approaches or embodiments, suitable polyisobutylene moieties may have an Mw / Mn of less than about 3.0, or less than about 2.8, or less than about 2.5, while in other approaches, suitable polyisobutylene substituents have a polydispersity of from about 1.5 to about 3.0, or from about 2.0 to about 3.0.

[0033] Suitable dicarboxylic acids or anhydrides for forming the dispersants herein can be selected from carboxylic reactants including the corresponding acid halides and C1-C4 aliphatic esters, such as maleic anhydride, maleic acid, fumaric acid, malic acid, tartaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, mesaconic acid, ethyl maleic acid, anhydride, dimethyl maleic anhydride, ethyl maleic acid, dimethyl maleic acid, hexyl maleic acid, etc. In some approaches, the molar ratio of dicarboxylic acid or anhydride to hydrocarbyl moieties 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, for example 3:1 to 1:3. In some embodiments, a particularly suitable molar ratio of acid or anhydride to hydrocarbyl moieties is 1:1 to less than 1.6:1. In other embodiments, other useful charge molar ratios of dicarboxylic acid or anhydride to hydrocarbyl moieties can 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 preparing the dispersant additives herein. Non-limiting exemplary polyamines can include aminoguanidine bicarbonate (AGBC), diethylene triamine (DETA), triethylene tetramine (TETA), tetraethylene pentamine (TEPA), pentaethylene hexamine (PEHA) and heavy polyamines. Heavy polyamines can include mixtures of polyalkylene polyamines with minor amounts of polyamine oligomers such as TEPA and PEHA, but with predominantly oligomers with 7 or more nitrogen atoms per molecule, 2 or more primary amines, and with more extensive 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 molar feed ratio of hydrocarbyl dicarboxylic acid or anhydride to 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 the reaction product of polyisobutenyl succinic anhydride (PIBSA) and a polyamine, such as a heavy polyamine, and the molar feed ratio of polyisobutenyl-substituted succinic anhydride to polyamine is from about 1.7:1 to about 2.5:1.

[0035] As noted above, the succinimide dispersants herein may be post-treated with a boron compound. Suitable boron compounds useful in forming the dispersants herein include any boron compound or mixture of boron compounds capable of introducing a boron-containing species into the ashless dispersant. Any boron compound, organic or inorganic, capable of undergoing such a reaction may be used. Thus, boron oxide, boron oxide hydrate, boron trifluoride, boron tribromide, boron trichloride, HBF4 boric acids such as boronic acids (e.g., alkyl-B(OH)2, or aryl-B(OH)2), boric acid (i.e., H3BO3), tetraboric acid (i.e., H2B5O7), metaboric acid (i.e., HBO2), ammonium salts of such boric acids, and esters of such boric acids may be used. The use of complexes of boron trihalides with ethers, organic acids, inorganic acids, or hydrocarbons is a convenient means of introducing the boron reactant into the reaction mixture. Such complexes are known and are exemplified by boron trifluoride-diethyl ether, boron trifluoride-phenol, boron trifluoride-phosphoric acid, boron trichloride-chloroacetic acid, boron tribromide-dioxane, and boron trifluoride-methyl ethyl ether.

[0036] The succinimide dispersants herein may also be post-treated with a phosphorus compound. Suitable phosphorus compounds for forming the dispersants herein include any phosphorus compound or mixture of phosphorus compounds capable of introducing phosphorus-containing species into the ashless dispersant. Thus, any phosphorus compound, organic or inorganic, capable of undergoing such a reaction may be used. Thus, such inorganic phosphorus compounds may be used as inorganic phosphoric acid and inorganic phosphorus oxides, including their hydrates. Exemplary organophosphorus compounds include full and partial esters of phosphoric acid, such as the mono-, di-, and triesters of phosphoric, thiophosphoric, dithiophosphoric, trithiophosphoric, and tetrathiophosphoric acids; mono-, di-, and triesters of phosphorous, thiophosphorous, dithiophosphorous, and trithiophosphorous acids; trihydrocarbyl phosphine oxides; trihydrocarbyl phosphine sulfides; mono- and dihydrocarbyl phosphonates, (RPO(OR')(OR"), where R and R' are hydrocarbyl and R" is a hydrogen atom or a hydrocarbyl group, and their mono-, di-, and trithio analogs; mono- and dihydrocarbyl phosphonites, (RP(OR')(OR"), where R and R' are hydrocarbyl and R" is a hydrogen atom or a hydrocarbyl group, is a hydrocarbyl group), and their mono- and dithio analogs. Thus, such compounds can be used, for example, as phosphorous acid (H3PO3, sometimes represented as H2(HPO3) and sometimes referred to as ortho-phosphorous acid or phosphoric acid), phosphoric acid (H3PO4, sometimes referred to as orthophosphoric acid), hypophosphoric acid (H4P2O6), metaphosphoric acid (HPO3), pyrophosphoric acid (H4P2O7), hypophosphorous acid (H3PO2, sometimes referred to as phosphinic acid), pyrophosphorous acid (H4P2O5, sometimes referred to as pyrophosphonic acid), phosphinous acid (H3PO), tripolyphosphoric acid (H5P3O10), tetrapolyphosphoric acid (H5P4O13), trimetaphosphoric acid (H3P3O9), phosphorus trioxide, phosphorus tetroxide, phosphorus pentoxide, and the like.Partial or full sulfur analogs such as phosphorotetrathioic acid (H3PS4), phosphoromonothioic acid (H3PO3S), phosphorodithioic acid (H3PO2S2), phosphorotrithioic acid (H3POS3), phosphorus sesquisulfide, phosphorus heptasulfide, and phosphorus pentasulfide (P2S5, sometimes referred to as P4S10) can also be used in forming dispersants for the present disclosure. Inorganic phosphorus halide compounds such as PCl3, PBr3, POCl3, PSCl3, etc. can also be used.

[0037] Similarly, organophosphorus compounds such as mono-, di-, and triesters of phosphoric acid (e.g., trihydrocarbyl phosphates, dihydrocarbyl monoacid phosphates, monohydrocarbyl diacid phosphates, and mixtures thereof), mono-, di-, and triesters of phosphorous acid (e.g., trihydrocarbyl phosphites, dihydrocarbyl hydrogen phosphites, hydrocarbyl diacid phosphites, and mixtures thereof), esters of phosphonic acids (both "primary" RP(O)(OR)2 and "secondary" RP(O)(OR)), esters of phosphinic acids, phosphonyl halides ( For example, RP(O)Cl2 and RP(O)Cl), halophosphates (e.g., (RO)PCl2 and (RO)PCl), halophosphites (e.g., ROP(O)Cl2 and (RO)2P(O)Cl), tertiary pyrophosphate esters (e.g., (RO)2P(O)-OP(O)(OR)2), and full or partial sulfur analogs of any of the foregoing organophosphorus compounds can be used, with each hydrocarbyl group containing 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. Halophosphines (e.g., hydrocarbyl phosphorus tetrahalides, dihydrocarbyl phosphorus trihalides, and trihydrocarbyl phosphorus dihalides), and halophosphines (monohalophosphines and dihalophosphines) can also be used.

[0038] In one embodiment, the fluid succinimide dispersants herein comprise at least a polyisobutenyl moiety having a number average molecular weight of at least about 2000, in another embodiment from about 2000 to about 3000, or in yet another embodiment from about 2000 to about 2300, and have from about 0.5 to about 1 weight percent nitrogen, from about 0.05 to about 0.25 weight percent boron, and from about 0.20 to about 0.45 weight percent phosphorous, or in yet another embodiment, a polyisobutenyl moiety having a number average molecular weight of at least 2000 to 2300, and have from about 0.60 to about 0.90 weight percent nitrogen, from about 0.10 to about 0.20 weight percent boron, and from about 0.25 to about 0.40 weight percent phosphorous.

[0039] In some embodiments, the dispersants described herein comprise from about 2 to about 8 weight percent (preferably from about 4 to about 8 weight percent) of an electric motor driveline fluid and deliver from about 300 to about 600 ppm nitrogen, from about 150 to about 270 ppm phosphorus, and from about 50 to about 120 ppm boron to the finished fluid. As shown in the examples below, when such succinimide dispersants are combined with other fluid components, particularly selected amounts of sulfur, boron, nitrogen, and / or phosphorus, the lubricants achieve acceptable wear and conductivity performance, and oxidation stability suitable for lubricants used in the drivelines or powertrains of electric and / or hybrid electric vehicles.

[0040] Sulfur Providing Additive The electric motor driveline fluid also includes a sulfur-providing additive in an amount that, when combined with the succinimide described above, improves wear performance, electrical conductivity, and oxidation stability. In any approach or embodiment herein, the sulfur-providing additive may be one or more thiadiazole compounds or hydrocarbyl-substituted derivatives thereof in an amount to provide at least about 1000 ppm sulfur to the lubricating fluid herein (preferably about 1000 to about 1500 ppm sulfur, more preferably about 1000 to about 1400 ppm sulfur, and most preferably about 1000 to about 1300 ppm sulfur). In another approach, 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-thiadiazoles are 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.

[0041] In some embodiments, the form and amount of the sulfur-providing additive herein contributes to the ability of the fluid to maintain low electrical conductivity and oxidative stability while also meeting other desirable wear performance characteristics. In this manner, the thiadiazole or derivative thereof comprises one or more compounds having the structure of formula III:

[0042] [ka] wherein each R1 in formula III is independently hydrogen or sulfur, each R2 in formula III is independently an alkyl group, n is an integer of 0 or 1, and when R1 is hydrogen, the integer n of adjacent R2 moieties is 0, and when R1 is sulfur, the integer n of adjacent R2 moieties is 1, with the proviso that at least one R1 is sulfur. In another approach, the thiadiazole additive is a blend of compounds of formula IIIa and formula IIIb shown below:

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

[0044] [ka] In formula IIIb, one integer n is 1 and the associated R2 group is a C5-C15 alkyl group (preferably a C8-C12 alkyl group), and the other integer n is 0 and both R1 are sulfur. In some embodiments, the sulfur-providing additive comprises a blend of formulas IIIa and IIIb, with formula Iva being the majority of the blend, and in other approaches, the blend of IIIa and IIIb is about 75 to about 90 weight percent IIIa and about 10 to about 25 weight percent IIIb (or other ranges therein). In another approach, the sulfur-providing additive is 2,5 dimercapto 1,3,4 thiadiazole, including 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 hydrocarbyl-substituted derivative thereof is present in the electric motor lubricating fluids herein in an amount to deliver 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 hydrocarbyl-substituted derivative thereof is present in the electric motor lubricating fluids herein in an amount to deliver 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 the thiadiazole compound or hydrocarbyl-substituted derivative thereof is present in the lubricating fluid in an amount to deliver from about 1000 to about 1300 ppm sulfur (or other ranges therein).

[0046] Friction modifiers In some embodiments, the electric motor driveline fluids herein contain only low levels of friction modifiers, particularly less than about 0.4 weight percent of friction modifiers. Herein, the electric motor driveline fluids contain less than about 0.4 weight percent of friction modifiers including alkylamides, alkylimides (having one or more alkyl C15-C30 alkyl chains), alkylamines, hydrocarbylamines, hydrocarbyl polyamines, hydrocarbyl imidazoles, derivatives thereof, or combinations thereof. In one embodiment, the electric driveline fluids herein may have friction modifiers, but may have less than about 0.3 weight percent of linear or branched C16-C18 substituted succinic acids or anhydrides reacted with ammonia. In another embodiment, the electric driveline fluids herein may contain up to about 0.3 weight percent of a linear or branched C16-C18 substituted succinic acid or anhydride reacted with an amine, polyamine, or ammonia, and / or 0 to about 0.05 weight percent of an alkyl or alkenyl substituted imidazoline, and / or 0 to about 0.08 weight percent of an ethoxylated alkylamine (preferably an ethoxylated tallow amine).

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

[0048] In other embodiments, the limited amounts of friction modifiers in the lubricants herein may also include minor amounts of any metal-containing and / or minor amounts of organic or metal-free friction modifiers, or may include only minor amounts 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 fatty compounds and olefins, sunflower oil and other naturally occurring vegetable or animal oils, dicarboxylic acid esters, esters or partial esters of a polyol and one or more aliphatic or aromatic carboxylic acids, and the like.

[0049] Friction modifiers, which tend to be limited in the electric driveline lubricants herein, may contain hydrocarbyl groups selected from linear, branched, or aromatic hydrocarbyl groups, or mixtures thereof, and such hydrocarbyl groups may be saturated or unsaturated. The hydrocarbyl groups may be composed of carbon and hydrogen or heteroatoms such as sulfur or oxygen. The hydrocarbyl groups may range from 12 to 25 carbon atoms. In some embodiments, the friction modifier may be a long chain fatty acid ester. In another embodiment, the long chain fatty acid ester may be a mono-ester, or a di-ester, or a (tri)glyceride. The friction modifier may 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 limited in the lubricants herein include organic, ashless (metal-free), nitrogen-free mechanical friction modifiers. Such friction modifiers include esters formed by reacting carboxylic acids and anhydrides with alkanols, and generally may contain polar end groups (e.g., carboxyl or hydroxyl) covalently bonded to an oleophilic hydrocarbon chain. An example of an organic ashless nitrogen-free friction modifier is generally known as glycerol monooleate (GMO), which may contain mono-, di-, and tri-esters of oleic acid. Other suitable friction modifiers are described in U.S. Pat. No. 6,723,685.

[0051] Amine-based friction modifiers may also be limited in the lubricants herein, and such friction modifiers may include amines or polyamines. Such compounds may have hydrocarbyl groups that are either saturated or unsaturated, linear, 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 may have hydrocarbyl groups that are linear, either saturated or unsaturated, or mixtures thereof. They may contain from about 12 to about 25 carbon atoms. Examples include ethoxylated amines and ethoxylated ether amines. The amines and amides may be used as such or in the form of adducts or reaction products with boron compounds such as boron oxides, boron halides, metaborates, boric acid, or mono-, di-, or tri-alkyl borates. Other suitable friction modifiers are described in U.S. Pat. No. 6,300,291.

[0052] In any embodiment herein, the lubricants herein, when present, comprise about 0.4 weight percent or less of total friction modifiers, particularly about 0.4 weight percent or less of friction modifiers of the types listed above. In some embodiments, the lubricants herein are substantially free of, or preferably free of, friction modifiers, meaning that the lubricants have about 0.4 weight percent or less of such friction modifiers, about 0.2 weight percent or less of friction modifiers, about 0.1 weight percent or less of friction modifiers, about 0.08 weight percent or less of friction modifiers, about 0.06 weight percent or less of friction modifiers, about 0.04 weight percent or less of friction modifiers, about 0.02 weight percent or less of friction modifiers, about 0.01 weight percent or less of friction modifiers, or no functional amounts of the above friction modifiers.

[0053] Base Oil The electric motor driveline fluids herein include one or more base oils having a lubricating viscosity. Base oils suitable for use in formulating electric motor lubricating fluids for use in electric and / or hybrid electric motor vehicles according to the present disclosure may be selected from any suitable synthetic or natural oil or mixtures thereof having a suitable lubricating viscosity. Natural oils may include animal oils, and vegetable oils (e.g., castor oil, lard oil), as well as mineral oils such as liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic, or mixed paraffinic-naphthenic types. Oils derived from coal or shale may also be suitable. Additionally, oils derived from gas-to-liquid processes are also suitable. The base oils 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 invention described herein may be a single base oil or a mixture of two or more base oils. One or more base oils may be selected from any of the base oils in Groups III or IV as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. Such base oil groups are shown in Table 1 as follows:

[0055] [Table 1]

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

[0057] API Group III base oils may 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 commonly referred to as gas-to-liquids (GTL). For example, the hydrocarbons may be hydroisomerized using the processes disclosed in U.S. Pat. Nos. 6,103,099 or 6,180,575, hydrocracked or hydroisomerized using the processes disclosed in U.S. Pat. Nos. 4,943,672 or 6,096,940, dewaxed using the methods disclosed in U.S. Pat. No. 5,882,505, or hydroisomerized and dewaxed using the processes disclosed in U.S. Pat. Nos. 6,013,171, 6,080,301, or 6,165,949.

[0058] PAOs, which are API Group IV base oils, are typically derived from monomers having 4 to 30, or 4 to 20, or 6 to 16 carbon atoms. Examples of PAOs that may be used in the present invention include those derived from octene, decene, mixtures thereof, and the like. The PAOs may have a kinematic viscosity at 100° C., as measured by ASTM D2270-10, of 2 to 15, or 3 to 12, or 4 to 8 cSt. Examples of PAOs include 4 cSt PAOs at 100° C., 6 cSt PAOs at 100° C., and mixtures thereof.

[0059] The base oil is combined with the 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 clutch. Thus, the base oil may be present in the lubricating fluid in an amount greater than about 80 weight percent, based on the total weight of the lubricating and cooling fluid. In some embodiments, the base oil may 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 driveline fluids described herein may contain, in addition to the components described above, other additives of the type used in electric motor fluid compositions, including, but not limited to, antioxidants, viscosity modifiers, phosphorus-containing components, detergents, corrosion inhibitors, rust inhibitors, antifoam agents, demulsifiers, pour point depressants, seal swell agents, as well as additional dispersants, additional friction modifiers, and additional sulfur-containing components.

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

[0062] Examples of phenolic antioxidants include 2,6-di-tert-butylphenol, liquid mixtures of tertiary butylated phenols, 2,6-di-tert-butyl-4-methylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 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 ring alkylated diphenylamines. Examples include sterically hindered tertiary butylated phenols, bisphenols, and cinnamic acid derivatives, and combinations thereof.

[0063] Aromatic amine antioxidants include those having the following formula:

[0064] [ka] (wherein R' and R" each independently represent a substituted or unsubstituted aryl group having 6 to 30 carbon atoms). Examples of the substituent on the aryl group include an aliphatic hydrocarbon group such as an alkyl group having 1 to 30 carbon atoms, a hydroxy group, a halogen radical, a carboxylic acid or ester group, or a nitro group.

[0065] The aryl groups are preferably substituted or unsubstituted phenyl or naphthyl, in particular where one or both of the aryl groups are substituted with at least one alkyl having from 4 to 30 carbon atoms, preferably from 4 to 18 carbon atoms, most preferably from 4 to 9 carbon atoms. It is preferred that one or both of the aryl groups are substituted, for example mono-alkylated diphenylamines, di-alkylated diphenylamines, or mixtures of mono- and di-alkylated diphenylamines.

[0066] Examples of diarylamines that may be used include, but are not limited to, diphenylamine; the 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, diheptyl-diphenylamine, p-oriented styrenated diphenylamines, mixed butyloctyldi-phenylamines, and mixed octylstyryldiphenylamines.

[0067] 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.

[0068] Alpha-olefins include, but are not limited to, any C4-C25 alpha-olefin. The alpha-olefins may be isomerized prior to or during the sulfurization reaction. Structural and / or conformational isomers of alpha-olefins containing internal double bonds and / or branching may also be used. For example, isobutylene is the branched olefin counterpart of the alpha-olefin 1-butene.

[0069] Sulfur sources that may be used in the sulfurization reaction of olefins include elemental sulfur, sulfur monochloride, sulfur dichloride, sodium sulfide, sodium polysulfide, and mixtures thereof added together at different stages of the sulfurization process.

[0070] Unsaturated oils, due to their unsaturation, can also be sulfurized and used as antioxidants. Examples of oils or fats that can be used include corn oil, canola oil, cottonseed oil, grapeseed oil, olive oil, palm oil, peanut oil, coconut oil, rapeseed oil, safflower seed oil, sesame seed oil, soybean oil, sunflower seed oil, tallow, and combinations thereof.

[0071] The total amount of antioxidant in the lubricating and cooling fluids described herein may be present in an amount to deliver up to about 200 ppm nitrogen, or up to about 150 ppm nitrogen, or up to about 100 ppm nitrogen.

[0072] Cleaning agents Metal detergents that may be included in the electric motor drive system fluids described herein generally comprise a polar head with a long hydrophobic tail, the polar head consisting of a metal salt of an acidic organic compound. The salts may contain substantially stoichiometric amounts of metal, in which case they are usually described as normal or neutral salts, and typically have a total base number or TBN (as measured by ASTM D2896) of 0 to less than 150. Large amounts of metal base may be included by reacting an excess of a metal compound, such as an oxide or hydroxide, with an acid gas, such as carbon dioxide. The resulting overbased detergent comprises micelles of neutralized detergent surrounding a core of inorganic metal base (e.g., hydrated carbonate). Such overbased detergents may have a TBN of about 150 or more, such as 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 may be present, such as both calcium and magnesium. Mixtures of calcium and / or magnesium with sodium may also be suitable. Suitable metal detergents may be overbased calcium or magnesium sulfonates with a TBN of 150-450 TBN, overbased calcium or magnesium phenates or sulfurized phenates with a TBN of 150-300 TBN, and overbased calcium or magnesium salicylates with a TBN of 130-350. 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 inhibitor 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 metals, based on the total weight of the lubricating and cooling fluid.

[0075] In one approach, the preferred detergent may be a neutral to low-based sulfonate, and in some approaches 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. Viscosity modifiers may include star polymers, suitable examples of which are described in U.S. Patent Application Publication No. 2012 / 0101017(A1).

[0077] The electric motor driveline 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) with an amine, amine-functionalized polymethacrylates, or esterified maleic anhydride-styrene copolymers reacted with amines.

[0078] 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.

[0079] Defoamer Antifoaming agents used to reduce or prevent the formation of stable foam include silicones, polyacrylates, or organic polymers. Antifoaming agents that may be useful in the compositions of the disclosed invention 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 may 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 Depressants The electric motor driveline fluid may optionally contain one or more pour point depressants. Suitable pour point depressants may include esters of maleic anhydride-styrene, polymethacrylates, polymethyl methacrylates, polyacrylates or polyacrylamides, or mixtures thereof. If present, the pour point depressant may be present in an amount of about 0.001% to about 0.04% by weight, based on the total weight of the lubricant.

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

[0082] [Table 2]

[0083] The percentages of each component above represent the weight percent 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 blend all of the components simultaneously using an additive concentrate (i.e., additives plus a diluent such as a hydrocarbon solvent). The use of an additive concentrate takes advantage of the mutual compatibility afforded by the combination of components when in the form of an additive concentrate. The use of a concentrate also reduces mixing time and the possibility of mixing errors. EXAMPLES

[0084] A better understanding of the present disclosure and its many advantages can be made clear with the following examples. The following examples are illustrative and are not intended to be limiting in 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 stated or apparent from the context of the following examples and discussion throughout this disclosure, all percentages, ratios, and parts described in this disclosure are by weight.

[0085] To demonstrate how the fluids herein achieve acceptable wear, oxidation stability, and electrical conductivity, the inventive fluids herein are compared to fluids having various elemental relationships of nitrogen, boron, sulfur, and / or phosphorus to evaluate wear, oxidation stability, and electrical conductivity. The formulations were evaluated for FZG scuffing, oxidation viscosity stability, and electrical conductivity. As shown in the table below, the inventive examples showed improved wear performance, electrical conductivity performance, and oxidation stability compared to the comparative examples. The inventive examples that had the required ingredients and were at the required treatment rates were therefore suitable for lubricating the drivelines of electric or hybrid electric vehicles. The comparative examples that delivered too much phosphorus, too much friction modifier, too much detergent, and / or contained too much dispersant derived from polyisobutylene with too low number average molecular weight had reduced wear performance, reduced oxidation stability, and / or reduced electrical conductivity, and therefore were not suitable for lubricating electric or hybrid electric vehicle drivelines. All fluids tested herein were considered low viscosity fluids, having a kV100°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 was performed in accordance with the A10 / 16.6R / 90 test of CEC L-84-02. The results are expressed in terms of failure load stages, with better results being obtained for samples with higher failure load stages. The inventive lubricants herein achieve a failure load stage of at least 8.

[0087] Oxidative viscosity stability was used to evaluate the difference between initial and final viscosity after the fluids were aged for 192 hours according to CEC L-48-A-00. Lower values ​​indicate improved performance. Thus, fluids with high oxidative stability exhibit only a small change 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 electric motor fluids to exhibit low electrical conductivity. Fluid conductivity was measured according to a modified version of ASTM D2624-15 (Testing of lubricants, not fuels) using a Flucon Epsilon+ at 1.5V, 20Hz and 170°C. The fluids herein have a conductivity of about 130nS / m or less.

[0089] The inventive and comparative examples tested in Table 3 below all contained various amounts of sulfurized components, friction modifiers, and dispersants as shown in Table 3. Otherwise, each fluid contained the same additional additives including antioxidants, antifoams, corrosion inhibitors, detergents, demulsifiers, and process oils. The inventive and comparative examples were tested with Group IV base oils to obtain final fluids having kinematic viscosities at 100°C as shown in the table below. The balanced delivery of sulfur, friction modifiers, and phosphorus delivered from the dispersant in the inventive examples 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 modifiers had reduced wear performance, or oxidation stability, and / or lubricant conductivity. Details of these components used in these examples are set forth below. Sulfur component (S-1) The 2,5-dimercapto-1,3,4-thiadiazole and / or its derivatives contained approximately 35% by weight of sulfur, and 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 phosphated and borated succinimide dispersant made from 950Mn polyisobutylene, maleic anhydride, a mixture of polyalkylene polyamines having an average of 6.5 nitrogen atoms per molecule, phosphoric acid, and boric acid. The dispersant contained approximately 0.76% by weight phosphorus, approximately 0.35% by weight boron, and approximately 1.75% by weight nitrogen. Dispersant 2 (Disp-2) A phosphated and borated succinimide dispersant made from 2100Mn polyisobutylene, maleic anhydride, a mixture of polyalkylene polyamines having an average of 6.5 nitrogen atoms per molecule, phosphoric acid, and boric acid. The dispersant had approximately 0.77% by weight nitrogen, about 0.15% by weight boron, and about 0.35% by weight phosphorus. Detergent Additive 1 (Det-1) An overbased calcium sulfonate having a TBN of about 300 and about 11.9 weight percent calcium. Friction modifier 1 (FM-1) 1-Hydroxy-2-heptadecenyl imidazoline Friction modifier 2 (FM-2) Branched C16-C18 substituted succinic acids or anhydrides reacted with ammonia. Friction modifier 3 (FM-3) Ethoxylated tallow alkylamines

[0090] [Table 3] * ASTM D445

[0091] [Table 4]

[0092] [Table 5] ** CEC L-84-02(A10 / 16.6R / 90) *** CEC L-48-A **** ASTM D2624-15 (20Hz, 170℃) was performed using a Fullcon Epsilon or equivalent tester.

[0093] Inventive Example 1 had acceptable FZG performance (8 or greater), improved oxidation performance (difference between initial viscosity and final viscosity after aging 0.5 cSt or less), and improved electrical conductivity (130 nS / m or less), while the comparative examples had either reduced FZG performance, reduced oxidation performance, and / or reduced electrical conductivity performance.

[0094] Inventive Example 2 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 with kinematic viscosities at 100°C as shown in the table below. Inventive Example 2 and Comparative Example 5 contained various amounts of friction modifiers and detergents as shown in Table 6 below. Otherwise, the examples contained similar amounts of additional additives including antioxidants, antifoams, demulsifiers, and process oils. The balanced delivery of sulfur, friction modifiers, and dispersants in Inventive Example 2 resulted in surprisingly improved wear, oxidation stability, and lubricant conductivity. Comparative Example 5 contained too much friction modifier and too much detergent, thus resulting in 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 derived from a mixture of 950 Mn polyisobutylene, 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 to 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. Antioxidants (AO): One or more antioxidants consisting of hindered phenols and alkylated diphenylamines

[0095] [Table 6] * ASTM D445

[0096] [Table 7]

[0097] [Table 8] ** CEC L-84-02(A10 / 16.6R / 90) *** CEC L-48-A **** ASTM D2624-15 (20Hz, 170℃) was performed using a Fullcon Epsilon or equivalent tester.

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

[0099] Although the lubricating compositions of the present disclosure have been described with reference to the detailed description and abstract herein, it should be understood that the foregoing description is intended to illustrate, and not to 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. It is intended that the specification and examples be considered as exemplary only, with the true scope of the present disclosure being 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 claims, "a" and / or "an" may refer to one or more than one. Unless otherwise indicated, all numbers expressing properties such as amounts of ingredients, molecular weights, percentages, ratios, reaction conditions, and the like, used herein, whether or not the term "about" is present, should be understood in all instances as being modified by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed at least in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0101] It is understood that each component, compound, substituent, or parameter disclosed herein should be construed as disclosed for use alone or in combination with one or more of any and all other components, compounds, substituents, or parameters disclosed herein.

[0102] It is further to be understood that each range disclosed herein should be construed as a disclosure of each particular value within the disclosed range having the same number of significant digits, thus a range of 1 to 4 should be construed as an explicit disclosure of any range of values ​​such as 1, 2, 3, and 4, as well as 1 to 4, 1 to 3, 1 to 2, 2 to 4, 2 to 3, etc.

[0103] It is further to be 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 a lower or upper limit of a range and therefore can be combined with any other lower or upper limit of a range or specific amount / value for the same component, compound, substituent, or parameter disclosed elsewhere in this application to form a range for that component, compound, substituent, or parameter.

Claims

1. 1. An electric driveline fluid comprising: one or more base oils of lubricating viscosity; a succinimide dispersant derived from polyisobutylene, said polyisobutylene having a number average molecular weight of 2000 or greater, said succinimide dispersant having up to 1 weight percent nitrogen and post-treated with a phosphorus-containing compound and a boron-containing compound to deliver 150 to 270 ppm of dispersant phosphorus (P) to said electric drive system fluid; a sulfur-providing additive comprising a thiadiazole or derivative thereof, said thiadiazole or derivative thereof providing at least 1000 ppm thiadiazole sulfur (S) to said electric driveline fluid; the combination of said dispersant phosphorus and said thiadiazole sulfur (P+S) is at least 1300 ppm and the weight ratio of said dispersant phosphorus to said thiadiazole sulfur (P / S) is at least 0.1; a detergent system providing one or more calcium-containing detergents, said one or more calcium-containing detergents providing 200 ppm or less of calcium; 0.4 weight percent or less of a friction modifier; Including, The friction modifier comprises an alkylimide, an alkylamine, a hydrocarbyl imidazole, a derivative thereof, or a combination thereof; the friction modifier optionally comprises an ethoxylated alkylamine in the range of up to 0.08 weight percent; the friction modifier optionally comprises, in the range of up to 0.4 weight percent, a linear or branched C16-C18 substituted succinic acid or anhydride reacted with an amine, polyamine, or ammonia; 1. An electric drive system fluid having a kV100 viscosity of 3.2 cSt or greater, a total phosphorus of 150-270 ppm, and an electrical conductivity of 130 nS / M or less measured at 20 Hz and 170° C. using said electric drive system fluid as measured by a modified electrical conductivity test in accordance with ASTM D2624-15: except for said electric powertrain fluids comprising an alkoxylated aliphatic amine delivering up to 20 ppm nitrogen to said electric powertrain fluid and an ether amine delivering up to 20 ppm nitrogen to said electric powertrain fluid.

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

3. 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.

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

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

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

3.

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

8. 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.

9. 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 polyisobutylene, the polyisobutylene having a number average molecular weight of 2000 or greater, the succinimide dispersant having up to 1 weight percent nitrogen and post-treated with a phosphorus-containing compound and a boron-containing compound to deliver 150 to 270 ppm of dispersant phosphorus (P) to the electric drivetrain fluid; and (iii) a succinimide dispersant providing at least 1000 ppm of thiadiazole sulfur (S) to the electric drivetrain fluid. (iv) a detergent system providing one or more calcium-containing detergents, the one or more calcium-containing detergents providing 200 ppm or less of calcium; and (v) 0.4 weight percent or less of a friction modifier, The friction modifier comprises an alkylimide, an alkylamine, a hydrocarbyl imidazole, a derivative thereof, or a combination thereof; the friction modifier optionally comprises an ethoxylated alkylamine in the range of up to 0.08 weight percent; the friction modifier optionally comprises, in the range of up to 0.4 weight percent, a linear or branched C16-C18 substituted succinic acid or anhydride reacted with an amine, polyamine, or ammonia; 20. A method of making a fluid for electrical driveline systems, comprising the steps of: providing an electrical driveline system having a kV100 viscosity of 3.2 cSt or greater; a total phosphorus content of 150-270 ppm; and an electrical conductivity of 130 nS / M or less measured at 20 Hz and 170° C. using said electrical driveline system fluid as measured by a modified electrical conductivity test in accordance with ASTM D2624-15; However, this does not include methods using said electric powertrain fluids comprising an alkoxylated aliphatic amine delivering up to 20 ppm nitrogen to said electric powertrain fluid and an ether amine delivering up to 20 ppm nitrogen to said electric powertrain fluid.

10. 10. The method of lubricating driveline components including electric motors as recited in claim 9, wherein the polyisobutylene has a number average molecular weight of 2000 to 2400 and / or the electric driveline fluid comprises 2 to 8 weight percent of the succinimide dispersant.

11. 10. The method of lubricating driveline components including electric motors as recited in claim 9, wherein the electric driveline fluid has an aging viscosity change of less than 0.5 cSt after the electric driveline fluid is aged according to CEC L-48-A.

12. 10. The method of lubricating driveline components including electric motors as recited in claim 9, wherein the electric driveline fluid achieves a failing load stage of at least 8 in the FZG A10 / 16.6R / 120 scuffing test of CEC L-84-02.

13. 90 to 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 10. The method of lubricating a driveline component including an electric motor as recited in claim 9, wherein: is sulfur.

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