Lubricating fluid for an electric motor

Abstract

An electric motor lubricating fluid for an electric motor system, the electric motor lubricating fluid comprising a lubricating base oil, a succinimide dispersant having a selected nitrogen cap agent, and an oil-soluble phosphorus anti-wear additive in an amount to promote effective performance of copper leaching and extreme pressure wear.

Description

Technical Field

[0001] This disclosure relates to methods of using lubricating fluids and lubricating fluids for electric motor systems. Specifically, the disclosed methods and compositions relate to lubricating fluids suitable for electric or hybrid electric vehicles, achieving low copper corrosion and conductivity, as well as high extreme pressure performance. Background Technology

[0002] A major challenge in developing lubricants for electric vehicle powertrains is achieving acceptable extreme pressure performance and conductivity while minimizing copper leaching to ensure compatibility with electronic components in the powertrain. In some formulations, uncapped succinimidyl dispersants tend to exhibit reduced extreme pressure performance and / or higher copper leaching. Certain types of capped dispersants, particularly those capped with boric acid, phosphorous acid, or phosphoric acid, tend to increase the fluid's electrical conductivity. Summary of the Invention

[0003] In one embodiment or method, this document describes an electric motor lubricating fluid suitable for electric or hybrid electric vehicles. In one aspect of this embodiment, the electric motor lubricating fluid comprises one or more base oils having a lubricating viscosity; an oil-soluble phosphorus anti-wear additive comprising ash-free dialkyl dithiophosphate, said oil-soluble phosphorus anti-wear additive providing the electric motor lubricating fluid with no more than about 200 ppm of sulfur; and a succinimide dispersant reaction product obtained by the following steps: (i) reacting a hydrocarbon-substituted dicarboxylic acid or anhydride with a polyalkylene polyamine to form an intermediate having at least one secondary amine; (ii) reacting the secondary amine with a capping agent comprising one or more of C6 or higher alkyl halides, acetic anhydride, and / or phenyl isocyanate; wherein the electric motor lubricating fluid contains less than about 300 ppm of total sulfur; and wherein the electric motor lubricating fluid substantially does not contain corrosion inhibitor additives.

[0004] In another embodiment or method, the electric motor lubricating fluid of the preceding paragraph may include one or more other characteristics in any combination. These other characteristics may include one or more of the following embodiments: wherein the electric motor lubricating fluid is substantially free of boron; and / or wherein the alkyl halide is an octyl halide; and / or wherein the octyl halide is an octyl bromide; and / or wherein the succinimide dispersant has a TBN of about 4 to about 25, and the succinimide dispersant provides about 1.0 to about 3.0 TBN to the electric motor lubricating fluid; and / or the electric motor lubricating fluid further comprises a sulfonate detergent, the amount of which contributes about 3 to about 50 TBN (ASTM A / B) to the electric motor lubricating fluid. D2896); and / or wherein the sulfonate detergent is calcium sulfonate, and the sulfonate detergent provides about 10 ppm to about 250 ppm of calcium to the electric motor lubricating fluid; and / or the electric motor lubricating fluid further comprises up to about 0.8% by weight of one or more amine antioxidants; and / or wherein the one or more amine antioxidants are selected from diarylamine antioxidants, diphenylamine; alkylated diphenylamine, 3-Hydroxydiphenylamine, N-phenyl-1,2-phenylenediamine, N-phenyl-1,4-phenylenediamine, Monobutyldiphenylamine, Dibutyldiphenylamine, Monooctyldiphenylamine, Dioctyldiphenylamine, Monononyldiphenylamine, Dinonyldiphenylamine, Monotetradecyldiphenylamine, Tetradecyldiphenylamine, Benzene-α-naphthylamine, Monooctylphenyl-α-naphthylamine, Benzene-β-naphthylamine, Monoheptyldiphenylamine, Diheptyldiphenylamine, p-Oriented Styrified Diphenylamine, Mixed Butyloctyldiphenylamine The electric motor lubricating fluid is substantially free of corrosion inhibitor additives selected from substituted or unsubstituted benzotriazole or triazole compounds, toluenetriazole compounds, corrosion inhibitors derived from monocarboxylic or polycarboxylic acids, alkenyl succinic acid or acid anhydride corrosion inhibitors, corrosion inhibitors derived from ether amines, acid phosphates, polyethoxylated compounds, imidazolines, or combinations thereof; and / or an oil-soluble phosphorus anti-wear additive comprising ashless dialkyl dithiophosphate is prepared by a method comprising the steps of: (a) reacting an organic hydroxyl compound with phosphorus pentasulfide to form a reaction product, and (b) further reacting the reaction product with an unsaturated carboxylic acid to form an oil-soluble phosphorus anti-wear additive comprising ashless dialkyl dithiophosphate; and / or wherein the ashless dialkyl dithiophosphate comprises a compound of formula I or a salt thereof.

[0005] (Formula IIa)

[0006] R4 and R5 are independently C1 to C1. 10The ashless dialkyl dithiophosphate comprises a straight-chain or branched alkyl group, and R6 is -H or -CH3; and / or wherein the ashless dialkyl dithiophosphate comprises 3-[[bis(2-methylpropoxy)thiophosphono]thio]-2-methylpropionic acid; and / or wherein the succinimide dispersant is post-treated with a capping agent that is substantially free of phosphorus compounds and / or substantially free of boron compounds; and / or wherein the electric motor lubricating fluid exhibits a copper leaching of about 100 ppm or less according to ASTM D130; and / or wherein the electric motor lubricating fluid has a destructive load grade of 8 or higher in the FZG A10 / 16.6R / 120 test of ASTM D5182; and / or wherein the electric motor lubricating fluid exhibits a conductivity of less than 25 nS / M at 100°C, measured using a modified conductivity test according to ASTM D2624-15 and measured at 20 Hz and 100°C.

[0007] In other methods or embodiments, this disclosure provides a method for lubricating a power transmission system component including an electric motor. In aspects of this embodiment, the method includes lubricating the power transmission system component with an electric motor lubricating fluid, wherein the electric motor lubricating fluid contacts portions of the electric motor. In other aspects of this embodiment, the electric motor lubricating fluid comprises: (a) one or more base oils having a lubricating viscosity; (b) an oil-soluble phosphorus anti-wear additive comprising ash-free dialkyl dithiophosphate, said oil-soluble phosphorus anti-wear additive providing the electric motor lubricating fluid with no more than about 200 ppm of sulfur; (c) a succinimide dispersant reaction product obtained by the following steps: (i) reacting a hydrocarbon-substituted dicarboxylic acid or anhydride with a polyalkylene polyamine to form an intermediate having at least one secondary amine, and (ii) reacting said secondary amine with a capping agent comprising one or more of C6 or higher alkyl halides, acetic anhydride, and / or phenyl isocyanate; and (d) wherein the electric motor lubricating fluid contains less than about 300 ppm of total sulfur; and wherein the electric motor lubricating fluid exhibits one or more of the following: copper leaching of about 100 ppm or less according to ASTM D130; FZG according to ASTM D5182. A10 / 16.6R / 120 test with a destructive load class of 8 or higher; and / or conductivity less than 25 nS / M at 100°C, measured using the electric motor lubricating fluid and measured at 20 Hz and 100°C, according to a modified conductivity test based on ASTM D2624-15.

[0008] In other methods or embodiments, the methods in the preceding paragraph may include one or more other features, steps, or embodiments in any combination. These other features, steps, or embodiments may include one or more of the following in any combination: wherein the electric motor lubricating fluid is substantially boron-free; and / or wherein the alkyl halide is an octyl halide; and / or wherein the octyl halide is an octyl bromide; and / or wherein the monosuccinimide dispersant or bissuccinimide dispersant has a TBN of about 4 to about 25, and the monosuccinimide dispersant or bissuccinimide dispersant provides the electric motor lubricating fluid with a TBN of about 1.0 to about 3.0; and / or the electric motor lubricating fluid further comprises a sulfonate detergent, the sulfonate detergent... The amount of the detergent contributes approximately 3 to approximately 50 TBN (ASTM D2896) to the lubricating fluid of the electric motor; and / or the sulfonate detergent is calcium sulfonate, and the sulfonate detergent provides approximately 10 ppm to approximately 250 ppm of calcium to the lubricating fluid of the electric motor; and / or the lubricating fluid of the electric motor further contains up to approximately 0.8 wt% of one or more amine antioxidants; and / or the one or more amine antioxidants are selected from diarylamine antioxidants, diphenylamine; alkylated diphenylamine, 3-hydroxydiphenylamine, N-phenyl-1,2-phenylenediamine, N-phenyl-1,4-phenylenediamine, monobutylamine, etc. Diphenylamine, dibutyldiphenylamine, monooctyldiphenylamine, dioctyldiphenylamine, monononyldiphenylamine, dinonyldiphenylamine, monotetradecyldiphenylamine, tetradecyldiphenylamine, benzyl-α-naphthylamine, monooctylphenyl-α-naphthylamine, benzyl-β-naphthylamine, monoheptyldiphenylamine, diheptyldiphenylamine, p-oriented styrylated diphenylamine, mixed butyloctyldiphenylamine, mixed octylstyryldiphenylamine, or combinations thereof; and / or the electric motor lubricating fluid is substantially free of corrosion inhibitor additives selected from substituted or unsubstituted benzotriazole or triazole compounds, tolyltriazole compounds, derivatives of monocarboxylic acids, or... Corrosion inhibitors of polycarboxylic acids, alkenyl succinic acid or anhydride corrosion inhibitors, corrosion inhibitors derived from etheramines, acidic phosphates, polyethoxylated compounds, imidazolines or combinations thereof; and / or oil-soluble phosphorus anti-wear additives comprising ashless dialkyl dithiophosphates are prepared by a method comprising the steps of: (a) reacting an organic hydroxyl compound with phosphorus pentasulfide to form a reaction product, and (b) further reacting the reaction product with an unsaturated carboxylic acid to form an oil-soluble phosphorus anti-wear additive comprising ashless dialkyl dithiophosphates; and / or wherein the ashless dialkyl dithiophosphate comprises a compound of formula I or a salt thereof:

[0009] (Formula IIa)

[0010] R4 and R5 are independently C1 to C1. 10The ashless dialkyl dithiophosphate comprises a straight-chain or branched alkyl group, and R6 is -H or -CH3; and / or wherein the ashless dialkyl dithiophosphate comprises 3-[[bis(2-methylpropoxy)thiophosphono]thio]-2-methylpropionic acid; and / or wherein the succinimide dispersant is post-treated with a capping agent that is substantially free of phosphorus-containing compounds and / or substantially free of boron-containing compounds.

[0011] In other embodiments, the use of any embodiment of the electric motor lubricating fluid of the present invention in the described compositions and / or methods is also provided for lubricating powertrain components of electric or hybrid electric vehicles and for achieving one or more of the following: copper leaching of about 100 ppm or less according to ASTM D130; achieving a destructive load class (FLS) of 8 or higher in the FZG A10 / 16.6R / 120 test of ASTM D5182; and / or achieving a conductivity of less than 25 nS / M at 100°C, measured at 20 Hz and 100°C, using the electric motor lubricating fluid according to the modified ASTM D2624-15.

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

[0013] Based on exemplary embodiments, this document describes an electric motor lubricating fluid suitable for electric or hybrid electric vehicles that achieves low copper leaching while also providing acceptable FZG destructive load level (FLS) wear performance and / or conductivity. It was found that when the lubricant also contains ashless dialkyl dithiophosphate, the choice of nitrogen-capping agent for the succinimide dispersant post-treatment unexpectedly affects not only copper leaching performance (e.g., ASTM D130), but also the extreme pressure properties of the lubricant (e.g., FZG A10 / 16.6R / 120 from ASTM D5182) and conductivity (e.g., ASTM D2624-15, at 20 Hz and 100 °C).

[0014] This application relates to the discovery that, by properly selecting a succinimide post-treatment end-capping agent, lubricating fluids suitable for electric vehicle powertrain systems can have improved copper leaching, extreme pressure performance, and / or electrical conductivity properties using end-capped succinimide dispersants. Specifically, this disclosure provides an electric motor lubricating fluid suitable for electric or hybrid electric vehicles, comprising at least: (a) one or more base oils having a lubricating viscosity; (b) an oil-soluble phosphorus anti-wear additive comprising ash-free dialkyl dithiophosphoric acid, said oil-soluble phosphorus anti-wear additive providing the electric motor lubricating fluid with sulfur not exceeding about 200 ppm; and (c) a succinimide dispersant reaction product obtained by the following steps: (i) reacting a hydrocarbon-substituted dicarboxylic acid or anhydride with a polyalkylene polyamine to form an intermediate having at least one secondary amine, and (ii) reacting the secondary amine with an end-capping agent selected from one or more of C6 or higher alkyl halides, acetic anhydride, and / or phenyl isocyanate. As discussed in more detail below, the selected post-treatment or capping agent forms alkyl capping groups, acetyl capping groups, and / or unsubstituted aniline capping groups, as derived from the respective capping agent. Preferably, the electric motor lubricating fluid of this disclosure also contains less than about 300 ppm of total sulfur, and in some embodiments, the electric motor lubricating fluid of this disclosure is substantially free of boron and / or substantially free of corrosion inhibitor additives. As used herein, substantially free of boron means that the electric motor lubricating fluid has less than about 10 ppm of boron, less than about 5 ppm of boron, or no functional amount of boron. Also as used herein, substantially free of corrosion inhibitor additives means that the electric motor lubricating fluid has less than about 0.002% by weight of corrosion inhibitor additives, less than about 0.001% by weight of corrosion inhibitor additives, or no functional amount of corrosion inhibitor additives.

[0015] Oil-soluble phosphorus anti-wear additives

[0016] In the method or implementation, the electric motor lubricating fluid of this invention also contains an oil-soluble phosphorus anti-wear additive in the form of ashless dialkyl dithiophosphate.

[0017] In one embodiment, the ashless dialkyl dithiophosphate additive provides the electric motor lubricating fluid with about 35 ppm to about 100 ppm of phosphorus (in other methods, about 45 ppm to about 90 ppm of phosphorus, or about 55 ppm to about 90 ppm of phosphorus, or about 55 ppm to about 75 ppm of phosphorus) and about 75 ppm to about 200 ppm of sulfur (in other methods, about 95 ppm to about 180 ppm of sulfur, about 95 ppm to about 160 ppm of sulfur, or about 120 ppm to about 160 ppm of sulfur). In some embodiments, the electric motor lubricating fluid herein comprises about 0.04 wt% to about 0.10 wt% of ashless dialkyl dithiophosphate (in other methods, about 0.05 wt% to about 0.09 wt%, or about 0.05 wt% to about 0.08 wt%, or about 0.06 wt% to about 0.08 wt%).

[0018] In one embodiment, the ashless dialkyl dithiophosphate has the structure of a compound of formula II or a salt thereof.

[0019] (Formula II)

[0020] In equation II above, R4 and R5 are each independently a straight chain or a branched chain C1 to C2. 10 Hydrocarbon group, and R7 in formula II is C1 to C2. 10 Straight-chain or branched carboxyl groups or C1 to C1 groups 10 A straight-chain or branched alkyl ester group of alkyl alkanoates. Preferably, R4 and R5 of Formula II are each C3 to C8 straight-chain or branched alkyl groups and R7 of Formula II is derived from 2-methylpropionic acid, such that the phosphorus product (or its salt) has the structure of Formula II:

[0021] (Formula IIa)

[0022] Where R4 and R5 are as defined relative to Equation II above, and are independently C1 to C... 10 Or a C3 to C8 straight-chain or branched alkyl group (preferably a branched C4 group), and R6 of Formula II above is -H or -CH3. In some methods or embodiments, the oil-soluble phosphorus anti-wear additive of the compositions and methods herein is preferably 3-[[bis(2-methylpropoxy)thiophosphono]thio]-2-methylpropionic acid.

[0023] In some methods, an oil-soluble phosphorus anti-wear additive comprising ashless dialkyl dithiophosphate is prepared by a method comprising the following steps: (a) reacting an organic hydroxy compound with phosphorus pentasulfide (in some forms, its monomer or dimer) to form a reaction product, and (b) further reacting the reaction product with an unsaturated carboxylic acid to form an oil-soluble phosphorus anti-wear additive comprising ashless dialkyl dithiophosphate.

[0024] Suitable organic hydroxyl compounds may include straight-chain alcohols, branched alcohols, hydroxyaryl compounds (such as phenol and naphthol), substituted aryl hydroxyl compounds (such as dipentylphenol), or any other hydroxyl organic material wherein the hydroxyl group will react with phosphorus pentasulfide. In one method, the starting alcohol is a saturated alcohol or a substituted aryl hydroxyl compound, such as an aryl hydroxyl compound substituted with a saturated alkyl radical. In some methods, the organic hydroxyl compound may be C1 to C2. 10 (In other methods, C1 to C6) straight-chain or branched alcohols, hydroxyaryl compounds, or mixtures thereof, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, sec-butanol, phenol, naphthol, pentanol, hexanol, isohexanol, octanol, decanol, dodecyl alcohol, octadecyl alcohol, 2-ethylhexanol, 4-methyl-2-pentanol, phenyl alcohol, butylphenyl alcohol, cyclohexanol, methylcyclopentanol, propenyl alcohol, butenyl alcohol, or combinations thereof. Preferred organic hydroxyl compounds herein include C1 to C4 alcohols, such as ethanol, propanol, or isopropanol, and most preferably, isobutanol.

[0025] Suitable unsaturated carboxylic acids that form the oil-soluble phosphorus anti-wear additives of this disclosure may include a wide variety of unsaturated carboxylic acids or fatty acids. Preferred unsaturated carboxylic acids may include C1 to C2. 20 Unsaturated fatty acids, such as acrylic acid, methacrylic acid, 2-ethylacrylic acid, or combinations thereof, with methacrylic acid being the most preferred. (As used herein, (meth)acrylic acid refers to acrylic acid or methacrylic acid.)

[0026] Succinimide dispersant

[0027] The electric motor lubricating fluid described herein also contains at least one oil-soluble ashless dispersant, which is a succinimide dispersant derived from a hydrocarbon-substituted dicarboxylic acid or anhydride reacting with a polyalkylene polyamine having at least one secondary amine, and wherein at least a portion of the secondary amine of the dispersant is post-treated with a selected end-capping agent. Suitable succinimide dispersants and their preparation are disclosed in at least US 7,897,696 and / or US 4,234,435, which are incorporated herein by reference. In embodiments, the succinimide dispersant is obtained by: (i) reacting a hydrocarbon-substituted dicarboxylic acid or anhydride with a polyalkylene polyamine to form an intermediate having at least one secondary amine, and (ii) reacting at least one secondary amine (or more) with an end-capping agent selected from one or more of C6 or higher alkyl halides, acetic anhydrides, and / or phenyl isocyanates. As discussed in more detail below, the selected capping agent forms alkyl capping groups, acetyl capping groups and / or unsubstituted aniline capping groups on the succinimide obtained from the respective capping agent.

[0028] In one embodiment, the hydrocarbon substituent of the succinimide dispersant herein has a number average molecular weight of about 500 to about 5000, or about 500 to about 2500. In one method of this embodiment, the hydrocarbon substituent of the succinimide dispersant herein is preferably derived from polyisobutylene having a number average molecular weight of about 900 to about 2500. In another method of this embodiment, the hydrocarbon substituent of the succinimide dispersant herein is preferably derived from polyisobutylene having a number average molecular weight of about 900 to about 1200, or in another embodiment about 2000 to about 2500. In any method or embodiment herein, the hydrocarbon portion of the hydrocarbon dicarboxylic acid or anhydride may be derived from a butene polymer, such as a polymer of isobutylene. Suitable polyisobutylenes used herein include those formed from conventional polyisobutylenes (e.g., PIBs having terminal double bonds of less than 50 mol%, less than 40 mol%, less than 30 mol%, less than 20 mol%, or less than 10 mol%) or alternatively highly reactive polyisobutylenes (e.g., HR-PIBs with terminal double bonds or terminal vinylidene content of greater than 50 mol%, greater than 60 mol%, greater than 70 mol%, greater than 80 mol%, or greater than 90 mol%). Suitable polyisobutylenes may include those prepared using a BF3 catalyst. As described below, molecular weights can be determined by gel permeation chromatography (GPC) using polystyrene (number-average molecular weight of 180 to about 18,000) as a calibration reference. The GPC method also provides information on the average weight molecular weight distribution; see, for example, WW Yau, JJ Kirkland, and DD Bly, “Modern Size Exclusion Liquid Chromatography,” John Wiley and Sons, New York, 1979, which is also incorporated herein by reference.

[0029] The polyisobutylene portion of any embodiment of the dispersant described herein may also have a molecular weight distribution (MWD) as determined by the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), also known as the polydispersity index (PDI). In some methods or embodiments, a suitable polyisobutylene portion may have a Mw / Mn ratio 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 1.5 to about 2.5.

[0030] The dicarboxylic acids or anhydrides suitable for forming dispersants described herein can be selected from carboxylic acid reactants, such as maleic anhydride, maleic acid, fumaric acid, malic acid, tartaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, mesoconic acid, ethyl maleic anhydride, dimethyl maleic anhydride, ethyl maleic acid, dimethyl maleic acid, hexyl maleic acid, etc., including the corresponding acidic halides and C1-C4 aliphatic esters. In some methods, the molar ratio of the dicarboxylic acid or anhydride to the hydrocarbon moiety in the reaction mixture used to prepare the hydrocarbon-dicarboxylic acid or anhydride can vary widely. Thus, the feed molar ratio can vary from 5:1 to 1:5, for example from 3:1 to 1:3. In some embodiments, a particularly suitable molar ratio of acid or anhydride to hydrocarbon moiety is 1:1 to less than 1.6:1. In other embodiments, the molar ratio of the dicarboxylic acid or anhydride to the hydrocarbon moiety may be 1:1 to 1.5:1, or 1:1 to 1.4:1, or 1.1:1 to 1.3:1, or 1:1 to 1.2:1.

[0031] Any of many polyalkylene polyamines can be used to prepare the dispersant additives described herein. Non-limiting exemplary polyamines may include aminoguanidine bicarbonate (AGBC), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), and / or polyamine substrates (e.g., heavy polyamines). Typical heavy polyamines may comprise mixtures of polyalkylene polyamines having small amounts of polyamine oligomers, such as TEPA and PEHA, but primarily oligomers having seven or more nitrogen atoms, two or more primary amines per molecule, and more extensive branching than conventional polyamine mixtures. Typically, these heavy polyamines have an average of 6.5 nitrogen atoms per molecule. Additional non-limiting polyamines that can be used to prepare hydrocarbon-substituted succinimide dispersants are disclosed in US 6,548,458, the disclosure of which is incorporated herein by reference in its entirety. In some embodiments, the feed molar ratio of a hydrocarbon-dicarboxylic acid or anhydride to a polyalkylene polyamine can be from about 1:1 to about 3.0:1. In one embodiment, the dispersant described herein can be a reaction product of polyisobutylene succinic anhydride (PIBSA) and a polyamine (e.g., a heavy polyamine), wherein the feed molar ratio of the polyisobutylene-substituted succinic anhydride to the polyamine is from about 1.7:1 to about 2.5:1.

[0032] As described above, embodiments of the succinimide dispersants suitable for the electric motor lubricating fluids described herein are post-treated with selected end-capping agents, and specifically, the succinimide dispersant(s)(one or more) secondary amines are post-treated with selected end-capping agents. As shown in the examples below, uncapped succinimide dispersants do not provide suitable performance in the context of corrosion and extreme pressure properties. Suitable end-capping agents for achieving performance in the context of lubricants for electric and hybrid electric vehicles that also contain ash-free dialkyl dithiophosphate include acetic anhydride, unsubstituted phenyl isocyanates, and / or C6 or higher (preferably C8) alkyl halides, such as octyl halides, like octyl bromide, etc. As shown in the examples, other end-capping agents cannot achieve the desired copper leaching, extreme pressure, and / or conductivity performance in the context of fluids that also contain ash-free dialkyl dithiophosphate. As mentioned above, the end-capping agents described herein are also substantially boron-free and phosphorus-free.

[0033] In embodiments, the method of post-processing any embodiment of the dispersant herein includes first forming a succinimide product as described above, and then further reacting the succinimide product with a selected post-processing agent. In some cases, the dispersant herein may be post-processed with more than one of the post-processing agents as described above, depending on the needs of various embodiments. In some embodiments, the formed capped or post-processed dispersant comprises a monosuccinimide dispersant or a bissuccinimide dispersant having one or more amine-substituted (from post-processing) groups from C6 or higher alkyl groups (derived from alkyl halide capping agents), acetyl groups (derived from acetic anhydride capping agents), and / or unsubstituted aniline groups (derived from phenyl isocyanate capping agents).

[0034] In the implementation scheme, examples of suitable dispersants herein include those of Formula III:

[0035] (Formula III)

[0036] In Formula III, R5 can be a hydrocarbon group having a molecular weight of about 500 to about 5000 (or any other range mentioned above), as described above; R6 of Formula III can be a divalent C1-C6 alkylene group; R7 of Formula III can be a divalent C1-C6 alkylene group; each of R8 and R9 of Formula III can independently be H, a C1-C6 alkyl group, or form a 5-membered or 6-membered ring with the N group to which they are attached (e.g., as in Formula IV below); and n can be an integer of 0, 1, 2, 3, 4, 5, 6, 7, or 8. When R8 and R9 of Formula III form a 5-membered or 6-membered ring with the N group to which they are attached, the portion has the structure of Formula IV below:

[0037] (Formula IV).

[0038] At least a portion (and in some embodiments, at most all) of the secondary nitrogen atom in Formula III is capped (e.g., post-treated to form an amine substitution), where ~ represents a bond linked to the nitrogen atom. Formula VIa represents aniline capping derived from a phenyl isocyanate capping agent; Formula VIb represents acetyl capping derived from an acetic anhydride capping agent; and Formula VIc represents alkyl capping derived from an alkyl halide capping agent, where w is an integer of 4 or greater (preferably 4 to 10, or 6 to 8, and most preferably 6):

[0039]

[0040] In the method, the dispersant as described herein may be used in the lubricating composition in an amount of about 0.5 wt% to about 2.0 wt%, or about 0.75 wt% to about 1.5 wt%, about 0.9 wt% to 1.25 wt%, or about 0.9 wt% to about 1.0 wt%, based on the final weight of the lubricating oil composition. In yet another embodiment, the succinimide dispersant of the electric motor lubricating fluid herein preferably has about 0.5 wt% to about 2.5 wt% nitrogen and provides the lubricant with about 70 ppm to about 300 ppm nitrogen (in other methods, about 80 ppm to about 250 ppm nitrogen from the dispersant, or about 150 ppm to about 300 ppm nitrogen from the dispersant).

[0041] Detergent

[0042] The electric motor lubricating fluid described herein may also contain one or more optional detergents. In one embodiment, the detergent is one or more neutral, low-alkaline, or over-alkaline sulfonate detergents (preferably calcium sulfonate detergents) having a total base number (TBN) of about 450 or less (preferably about 0 to about 450), and is provided in an amount to the electric motor lubricating fluid to contribute about 3 to about 50 TBN to the electric motor lubricating fluid (in other methods, about 3 to about 30, about 3 to about 10, about 3 to about 8, or about 3 to about 5 TBN), and wherein the TBN is measured according to ASTM D2896. Suitable detergents and methods of their preparation are described in more detail, for example, in several patent publications, including US 7,732,390; US 4,165,291 and / or US 4,206,062 (and references cited therein), which are incorporated herein by reference.

[0043] As used herein, low-alkaline to neutral detergent additives may have a total base number (TBN) of less than about 200 mg KOH / g (preferably less than about 100 mg KOH / g, less than about 50 mg KOH / g, or less than about 30 mg KOH / g, and may be from about 0 mg KOH / g to about 200 mg KOH / g), and over-alkaline detergents may have a total base number (TBN) of about 200 mg KOH / g or greater, or about 250 mg KOH / g or greater, or about 300 mg KOH / g or greater, or about 375 mg KOH / g or greater, or about 400 mg KOH / g or greater (wherein the TBN is measured by ASTM D2896) (in other embodiments, about 200 mg KOH / g to about 450 mg KOH / g or other ranges therewith). In other embodiments, the overly alkaline detergent may have a metal-to-matrix ratio of 1.1:1 or less, or 2:1 or less, or 4:1 or less, or 5:1 or less, or 7:1 or less, or 10:1 or less, or 12:1 or less, or 15:1 or less, or 20:1 or less.

[0044] In embodiments, a suitable detergent matrix (preferably a sulfonic acid detergent) may be salted with an alkali metal or alkaline earth metal, preferably calcium and / or magnesium, and most preferably calcium. Thus, suitable detergents may comprise alkali metal or alkaline earth metal salts of petroleum sulfonic acids and long-chain mono- or dialkyl aryl sulfonic acids, wherein the aryl group is benzyl, tolyl, or xylyl. Examples of suitable detergents found to have effective properties favorable to toluene triazole corrosion inhibitors and oil-soluble ashless dialkyl dithiophosphate extreme pressure additives include calcium sulfonate and / or magnesium sulfonate, and preferably calcium sulfonate.

[0045] Overly alkaline detergent additives are also well known in the art and generally include alkali metal or alkaline earth metal overly alkaline detergent additives. Such detergent additives are prepared by reacting a metal oxide or metal hydroxide with a matrix and carbon dioxide gas. The matrix is ​​typically an acid, for example, in the context of lubricants herein, an acid such as an aliphatic-substituted sulfonic acid. The term “overly alkaline” refers to metal salts, such as metal salts of sulfonic acids used in the fluids herein, in which the amount of metal present exceeds the stoichiometric amount. Such salts can have conversion levels exceeding 100% (i.e., they can contain more than 100% of the theoretical amount of metal required to convert the acid to its “normal” or “neutral” salt). The expression “metal ratio” is often abbreviated as MR, which is used to represent the ratio of the total stoichiometric amount of metal in a highly alkaline salt to the stoichiometric amount of metal in a neutral salt, based on known chemical reactivity and stoichiometry. In normal or neutral salts, the metal ratio is one, while in highly alkaline salts, MR is greater than one. They are often referred to as highly alkaline, hyperalkaline, or superalkaline salts and can be salts of organic sulfuric acid.

[0046] When such detergent compositions are formed in an inert diluent (e.g., process oil, typically mineral oil), the total base number reflects the alkalinity of the overall composition, which includes the diluent and any other materials that may be present in the detergent composition (e.g., accelerators, etc.).

[0047] Preferably, the detergent described herein is a neutral, low-alkaline, or over-alkaline calcium sulfonate detergent, and wherein the detergent provides about 10 ppm to about 250 ppm of a metal (in other embodiments, about 20 ppm to about 200 ppm of a metal, about 25 ppm to about 160 ppm of a metal, or about 30 ppm or about 100 ppm of a metal). The detergent metal may be calcium, magnesium, and / or sodium, but is preferably calcium. Preferably, the detergent is a neutral to low-alkaline calcium sulfonate.

[0048] antioxidants

[0049] In some embodiments, the methods and lubrication compositions described herein may also include an optional antioxidant compound (or blend thereof) comprising one or more phenolic antioxidant compounds, one or more amine antioxidant compounds, or combinations thereof. In some embodiments, for example, the methods and lubrication compositions described herein comprise one or more phenolic antioxidant compounds and one or more amine antioxidant compounds. Preferably, the electric motor lubricating fluid contains at least an amine antioxidant.

[0050] In one method or embodiment, the amine antioxidant may include, but is not limited to, antioxidants selected from aromatic amines, alkylated diphenylamines, phenyl-α-naphthylamines, alkylated phenyl-α-naphthylamines, hindered non-aromatic amines, or combinations thereof. In some methods, the methods and lubricating compositions described herein may contain up to about 0.8% by weight of an amine antioxidant, or in other embodiments, about 0.6% to about 0.4% by weight of an amine antioxidant.

[0051] In some methods, the amine antioxidant can be one or more aromatic amine antioxidants, and can include, but is not limited to, diarylamines having the following formula:

[0052]

[0053] In the above formula, R' and R'' each independently represent a substituted or unsubstituted aryl group having 6 to 30 carbon atoms. If substituted, suitable substituents for the aryl groups of R' and R'' include aliphatic hydrocarbon groups such as alkyl groups having 1 to 30 carbon atoms, hydroxyl groups, halogen groups, carboxylic acid or ester groups, or nitro groups. The aryl group can be a substituted or unsubstituted phenyl or naphthyl group, particularly wherein one or both of these aryl groups are substituted with at least one alkyl group having 4 to 30 carbon atoms, preferably 4 to 18 carbon atoms, and most preferably 4 to 9 carbon atoms. In the method, one or both aryl groups can be substituted, for example, monoalkylated diphenylamine, dialkylated diphenylamine, C9 alkylated diphenylamine, or a mixture of monoalkylated diphenylamine and dialkylated diphenylamine.

[0054] Examples of diarylamine antioxidants that may be used include, but are not limited to: diphenylamine; various alkylated diphenylamines, 3-hydroxydiphenylamine, N-phenyl-1,2-phenylenediamine, N-phenyl-1,4-phenylenediamine, monobutyldiphenylamine, dibutyldiphenylamine, monooctyldiphenylamine, dioctyldiphenylamine, monononyldiphenylamine, dinonyldiphenylamine, monotetradecyldiphenylamine, tetradecyldiphenylamine, benzene-α-naphthylamine, monooctylphenyl-α-naphthylamine, benzene-β-naphthylamine, monoheptyldiphenylamine, diheptyldiphenylamine, p-oriented styrylated diphenylamine, mixed butyloctyldiphenylamine and mixed octylstyryldiphenylamine.

[0055] The compositions described herein may also include, optionally, a phenolic antioxidant. Suitable phenolic or hindered phenolic antioxidants may contain sec-butyl and / or tert-butyl groups as sterically hindered groups. The phenolic group may also be substituted with a hydrocarbon group and / or a bridging group attached to a second aromatic group. Examples of suitable phenolic or hindered phenolic antioxidants include 2,6-di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol, 4-propyl-2,6-di-tert-butylphenol, or 4-butyl-2,6-di-tert-butylphenol, or 4-dodecyl-2,6-di-tert-butylphenol. In one embodiment, the hindered phenolic antioxidant may be an ester and may include, for example, Irganox, available from BASF. ™ L-135 may be an addition product derived from 2,6-di-tert-butylphenol and an alkyl acrylate, wherein the alkyl group may contain about 1 to about 18, or about 2 to about 12, or about 2 to about 8, or about 2 to about 6, or about 4 carbon atoms. Another commercially available hindered phenolic antioxidant may be an ester and may include Ethanox, available from Albemarle Corporation. ™4716. In some methods, the methods and lubricating compositions described herein may contain (if used) up to about 0.8% by weight of a phenolic antioxidant or, in other embodiments, up to about 0.6% by weight or up to about 0.4% by weight of a phenolic antioxidant.

[0056] base oil :

[0057] The electric motor lubricating fluid described herein comprises one or more base oils having a lubricating viscosity. The base oil or base oil having a lubricating viscosity suitable for formulating the electric motor lubricating fluid for electric and / or hybrid electric motor vehicles according to this disclosure may be selected from any of suitable synthetic or natural oils or mixtures thereof having a suitable lubricating viscosity. Natural oils may include animal and vegetable oils (e.g., castor oil, lard) and mineral oils, such as liquid petroleum and solvent-treated or acid-treated alkanes, naphthenes, or mixed alkanes-naphthenes type mineral lubricants. Oils derived from coal or shale may also be suitable. Furthermore, oils derived from gas-to-liquid processes are also suitable. As measured by ASTM D2270-10, the base oil may have a kinematic viscosity of about 2 cSt to about 15 cSt at 100°C (e.g., kV100).

[0058] The base oils used in this invention 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 base oil in Group III or IV as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guide. These base oil classes are shown in Table 1 below:

[0059] Table 1

[0060]

[0061] In one embodiment, the base oil may be selected from API GII base oils, API Group III base oils, or API Group IV base oils, or mixtures of these base oils. Alternatively, the base oil may be two or more of API Group II base oils, two or more of API GIII base oils, or two or more of API Group IV base oils.

[0062] API Group III base oils may include oils derived from Fischer-Tropsch synthetic hydrocarbons. Fischer-Tropsch synthetic hydrocarbons are prepared from syngas containing H2 and CO using a Fischer-Tropsch catalyst. These hydrocarbons typically require further processing before use as base oils. These types of oils are commonly referred to as gas-to-liquid (GTL) oils. For example, the hydrocarbons can be hydroisomerized using the methods disclosed in U.S. Patent 6,103,099 or 6,180,575; hydrocracking and hydroisomerized using the methods disclosed in U.S. Patent 4,943,672 or 6,096,940; dewaxing using the methods disclosed in U.S. Patent 5,882,505; or hydroisomerized and dewaxing using the methods disclosed in U.S. Patent 6,013,171, 6,080,301; or 6,165,949.

[0063] API Group IV base oils, PAOs, are typically derived from monomers having 4 to 30, 4 to 20, or 6 to 16 carbon atoms. Examples of PAOs that can be used in this invention include those derived from octene, decene, mixtures thereof, etc. As measured by ASTM D2270-10, PAOs can have a kinematic viscosity of 2 to 15, 3 to 12, or 4 to 8 cSt at 100°C. Examples of PAOs include PAOs with a viscosity of 4 cSt at 100°C, PAOs with a viscosity of 6 cSt at 100°C, and mixtures thereof.

[0064] The base oil is combined with additive compositions as disclosed in the embodiments herein to provide lubricating and cooling fluids for use in electric motor systems having electric motors, gears, and clutches. Therefore, the base oil may be present in the lubricating and cooling fluids in an amount greater than about 80% by weight, based on the total weight of the lubricating and cooling fluids. In some embodiments, the base oil may be present in the lubricating and cooling fluids in an amount greater than about 85% by weight, based on the total weight of the lubricating and cooling fluids.

[0065] Other additives

[0066] In addition to the components described above, the electric motor lubricating fluid described herein may also contain other additives of the type used in electric motor lubricating fluid compositions. However, as stated above, the electric motor lubricating fluid is substantially free of corrosion inhibitors. In embodiments, the electric motor lubricating fluid described herein is substantially free of corrosion inhibitor additives selected from substituted or unsubstituted benzotriazole or triazole compounds, tolyltriazole compounds, corrosion inhibitors derived from monocarboxylic or polycarboxylic acids, alkenyl succinic acid or acid anhydride corrosion inhibitors, corrosion inhibitors derived from ether amines, acid phosphates, polyethoxylated compounds, imidazolines, or combinations thereof.

[0067] These optional additives include, but are not limited to, additional antioxidants, viscosity modifiers, phosphorus-containing components, defoamers, demulsifiers, pour point depressants, sealing swelling agents, friction modifiers, and sulfur-containing components.

[0068] Antioxidants: In some embodiments, the lubricating fluid for electric motors contains one or more other antioxidants. Besides the antioxidants discussed above, suitable other antioxidants include sulfur-containing antioxidants and organophosphites, etc.

[0069] 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., those with an average molecular weight of 168 g / mol to 351 g / mol) are preferred. Examples of olefins that can be used include α-olefins, isomerized α-olefins, branched olefins, cycloolefins, and combinations thereof.

[0070] α-olefins include, but are not limited to, any C4 to C5 olefins. 25 α-Alkenes. α-Alkenes can be isomerized before or during sulfidation. Structural and / or conformational isomers of α-alkenes containing internal double bonds and / or branches can also be used. For example, isobutene is a branched alkene counterpart of the α-alkene 1-butene.

[0071] Sulfur sources that can be used in olefin sulfidation reactions include elemental sulfur, sulfur monochloride, sulfur dichloride, sodium sulfide, sodium polysulfide, and mixtures thereof, either together or added at different stages of the sulfidation process.

[0072] 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 oil, sesame oil, soybean oil, sunflower oil, tallow, and combinations thereof.

[0073] In some embodiments, the total amount of antioxidant in the lubricating fluid described herein may be delivered in amounts of up to about 200 ppm of nitrogen, or up to about 150 ppm of nitrogen, or about 100 ppm to about 150 ppm of nitrogen.

[0074] Friction modifiers: In some embodiments, the lubricating fluid of the electric motor contains a friction modifier. Suitable additional friction modifiers may include metal-containing and metal-free friction modifiers, and may include, but are not limited to, imidazolines, amides, amines, succinimides, alkoxylated amines, alkoxylated ether amines, amine oxides, amides, nitriles, betaine, quaternary ammonium, imines, amine salts, aminoguanidines, enolamides, phosphonates, metal-containing compounds, glycerides, sulfurized aliphatic compounds and olefins, sunflower oil, other naturally occurring vegetable or animal oils, dicarboxylic acid esters, polyols and esters or metaesters of one or more aliphatic or aromatic carboxylic acids, etc.

[0075] Suitable friction modifiers may contain a hydrocarbon group selected from straight-chain, branched, or aromatic hydrocarbon groups or mixtures thereof, and such hydrocarbon groups may be saturated or unsaturated. The hydrocarbon group may consist of carbon and hydrogen or heteroatoms (such as sulfur or oxygen). The hydrocarbon group may have between 12 and 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 monoester, diester, or (tri)glycerol ester. 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.

[0076] Other suitable friction modifiers may include organic, ashless (metal-free), nitrogen-free organic friction modifiers. Such friction modifiers may comprise esters formed by reacting carboxylic acids and anhydrides with alkanols, and typically contain polar terminal groups (e.g., carboxyl or hydroxyl groups) covalently bonded to a lipophilic hydrocarbon chain. Examples of organic ashless and nitrogen-free friction modifiers are generally known as glyceryl monooleate (GMO), which may contain monoesters, diesters, and trimers of oleic acid. Other suitable friction modifiers are described in U.S. Patent No. 6,723,685.

[0077] Amine-based friction modifiers may include amines or polyamines. These compounds may have straight-chain saturated or unsaturated hydrocarbon groups or mixtures thereof, and may contain 12 to 25 carbon atoms. Other examples of suitable friction modifiers include alkoxylated amines and alkoxylated ether amines. These compounds may have linear chains, saturated or unsaturated hydrocarbon groups, or mixtures thereof. They may contain about 12 to about 25 carbon atoms. Examples include ethoxylated amines and ethoxylated ether amines.

[0078] Amines and amides may be used as is or as additions or reaction products with boron compounds, such as boron oxide, boron halide, metaborates, boric acids or monoalkyl, dialkyl, or trialkyl esters of borate. Other suitable friction modifiers are described in U.S. Patent 6,300,291.

[0079] If the additional friction modifier contains nitrogen, such additional friction modifier can be present in the lubricating fluid in any amount, as long as it does not impair performance requirements.

[0080] Viscosity modifiers: The lubricating fluid for electric motors may optionally contain one or more viscosity modifiers. Suitable viscosity modifiers may include polyolefins, olefin copolymers, ethylene / propylene copolymers, polyisobutylene, hydrogenated styrene-isoprene polymers, styrene / maleate copolymers, hydrogenated styrene / butadiene copolymers, hydrogenated isoprene polymers, α-olefin maleic anhydride copolymers, polymethyl methacrylates, polyacrylates, polyalkylstyrene, hydrogenated alkenylaryl conjugated diene copolymers, or mixtures thereof. Viscosity modifiers may include star polymers, and suitable examples are described in U.S. Publication 2012 / 0101017 A1.

[0081] In addition to viscosity modifiers or alternatives to viscosity modifiers, the electric motor lubricating fluids described herein may optionally contain one or more dispersant viscosity modifiers. Suitable dispersant viscosity modifiers may include functionalized polyolefins, such as ethylene-propylene copolymers functionalized with the reaction product of an acylation agent (such as maleic anhydride) and an amine; amine-functionalized polymethacrylates; or esterified maleic anhydride-styrene copolymers reacted with an amine.

[0082] The total amount of viscosity modifier and / or dispersant (if present) may be up to about 2.0% by weight, or up to about 1.5% by weight, or up to about 0.5% by weight, based on the total weight of the lubricating fluid.

[0083] Demulsifiers: Demulsifiers include trialkyl phosphates, and various polymers and copolymers of ethylene glycol, ethylene oxide, propylene oxide, or mixtures thereof, including polyethylene oxide, polypropylene oxide, and (ethylene oxide-propylene oxide) polymers. When present, the amount of demulsifier in the lubricating and cooling fluid may be up to about 0.05% by weight, up to about 0.02% by weight, or less than about 0.015% by weight, based on the total weight of the lubricating fluid.

[0084] Defoamers: Defoamers used to reduce or prevent the formation of stable foams include silicones, polyacrylates, or organic polymers. Foam inhibitors that can be used in the compositions of the disclosed invention include polysiloxanes, copolymers of ethyl acrylate and 2-ethylhexyl acrylate, and optionally vinyl acetate. When present, the amount of defoamer in the lubricating and cooling fluid may be at most about 0.1% by weight, or at most about 0.05% by weight, or less than about 0.04% by weight, based on the total weight of the lubricating fluid.

[0085] Pour point depressant: The lubricating fluid for electric motors may optionally contain one or more pour point depressants. Suitable pour point depressants may include maleic anhydride-styrene esters, polymethyl methacrylates, polyacrylates, polyacrylic acid esters, or polyacrylamide, or mixtures thereof. Based on the total weight of the lubricant, the pour point depressant (if present) may be present in an amount from about 0.001% by weight to about 0.04% by weight.

[0086] Generally, the lubricating fluids described herein may contain additive components within the range listed in Table 2.

[0087] Table 2

[0088]

[0089] The percentages for each component above represent the weight percentage of each component based on the total weight of the lubricating fluid containing said component. Additives used to formulate the compositions described herein can be blended into the base oil individually or in various sub-combinations. However, it may be suitable to simultaneously blend all components using an additive concentrate (i.e., an additive plus a diluent, such as a hydrocarbon solvent). The use of an additive concentrate utilizes the compatibility offered by the combination of components in additive concentrate form. Furthermore, the use of the concentrate reduces blending time and the possibility of blending errors.

[0090] In various embodiments, the electric motor lubricant of this paper achieves a destructive load level of at least 8 (e.g., FLS) in the FZG A10 / 16.6R / 120 wear test according to ASTM D5182, and exhibits copper leaching of approximately 100 ppm or less when measured according to ASTM D130-19 (e.g., a semi-immersed copper strip heated to 150°C for 168 hours); and achieves a conductivity of less than 25 nS / M using the electric motor lubricant in a conductivity test according to a modified ASTM D2624-15, measured at 20 Hz and 100°C. Surprisingly, the selection of the end-capping agent for the dispersant contributes to achieving these performance characteristics even in electric motor lubricants that also contain ashless dialkyl dithiophosphate.

[0091] Selected definition:

[0092] Unless the context of this discussion indicates otherwise, the following definitions of terms are provided to clarify the meaning of certain terms as used herein.

[0093] The terms “lubricating oil,” “lubricant composition,” “lubricating composition,” “lubricant,” “electric motor lubricating fluid,” and “lubricating fluid” refer to finished lubricating products comprising a major amount of a base oil and a minor amount of an additive composition. As used herein, “major amount” includes at least 50% by weight (at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight), and “minor amount” includes less than 50% by weight.

[0094] As used herein, the terms “additive package,” “additive concentrate,” and “additive composition” refer to a portion of a lubricating oil composition that does not include a major amount of base oil.

[0095] As used herein, the term "hydrocarbon substituent" or "hydrocarbon group" is used in its common sense, as is well known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly connected to the rest of the molecule and having predominantly hydrocarbon characteristics. Each hydrocarbon group is independently selected from hydrocarbon substituents and hydrocarbon substituents containing one or more of a halogen group, hydroxyl group, alkoxy group, mercapto group, nitro group, nitroso group, amino group, pyridyl group, furanyl group, imidazolyl group, oxygen, and nitrogen, and wherein there are no more than two non-hydrocarbon substituents present for every ten carbon atoms in the hydrocarbon group.

[0096] As used herein, unless otherwise expressly stated, the terms “weight percentage” or “weight %” mean the percentage of the said component by weight of the whole composition.

[0097] As used herein, the terms “soluble,” “oil-soluble,” or “dispersible” may, but do not necessarily, mean that a compound or additive is soluble, miscible, or capable of being suspended in oil in all proportions. However, the foregoing terms do mean that they are, for example, soluble, suspended, dispersible, or stably dispersed in oil to a degree sufficient to exert their intended effect in an environment where oil is used. Furthermore, if desired, additional admixtures may be permitted at higher levels of specific additives.

[0098] As used herein, the term "alkyl" refers to a straight-chain, branched, cyclic, and / or substituted saturated chain moiety of about 1 to about 200 carbon atoms.

[0099] As used herein, the term "alkenyl" refers to a straight-chain, branched, cyclic, and / or substituted unsaturated chain portion of about 3 to about 30 carbon atoms.

[0100] As used herein, the term "aryl" refers to monocyclic and polycyclic aromatic compounds, which may include alkyl, alkenyl, alkylaryl, amino, hydroxyl, alkoxy, halogen substituents and / or heteroatoms including but not limited to nitrogen and oxygen.

[0101] As used herein, “number-average molecular weight” or “Mn” is determined by gel permeation chromatography (GPC) using commercially available polystyrene standards (where Mn is from about 180 to about 18,000 as a calibration reference). For example, the molecular weight (Mn) of any embodiment described herein can be determined using an instrument such as a gel permeation chromatography (GPC) instrument from Waters, and the data can be processed using software such as WatersEmpower software. GPC instruments may be equipped with a Waters separation module and a Waters refractive index detector (or similar optional equipment). GPC operating conditions may include a guard column, four Agilent PLgel columns (300 × 7.5 mm in length; 5 µm in particle size and pore size ranging from 100 Å to 10,000 Å), and a column temperature of about 40 °C. Unstabilized HPLC-grade tetrahydrofuran (THF) can be used as a solvent at a flow rate of 1.0 mL / min. GPC instruments can be calibrated using commercially available polystyrene (PS) standards with a narrow molecular weight distribution ranging from 500 g / mol to 380,000 g / mol. For samples with a mass less than 500 g / mol, calibration curves can be extrapolated. Samples and PS standards can be dissolved in THF and prepared at concentrations from 0.1 wt% to 0.5 wt% and are ready for use without filtration. GPC measurements are also described in US 5,266,223, which is incorporated herein by reference. GPC methods also provide molecular weight distribution information; see, for example, WW Yau, JJ Kirkland, and DD Bly, “ModernSize Exclusion Liquid Chromatography”, John Wiley and Sons, New York, 1979, which is also incorporated herein by reference.

[0102] Unless otherwise stated, total base number (TBN) is measured according to ASTM D2896.

[0103] It should be understood that throughout this disclosure, the terms “comprising,” “including,” “containing,” etc., are considered open-ended and include any element, step, or ingredient not expressly listed. The phrase “consisting substantially of…” means including any expressly listed element, step, or ingredient, as well as any additional element, step, or ingredient that does not substantially affect the basic and novel aspects of the invention. This disclosure also considers that any composition described using the terms “comprising,” “including,” or “containing” is also to be interpreted as including the disclosure of the same composition “consisting substantially of its specifically listed components” or “consisting of its specifically listed components.”

[0104] Example

[0105] The present disclosure and its many advantages can be better understood through the following examples. These examples are illustrative and do not limit its scope or spirit. Those skilled in the art will readily understand that variations of the components, methods, steps, and apparatus described in these examples can be used. All percentages, ratios, and parts mentioned in this disclosure are by weight, unless otherwise stated or apparent from the context of the following examples and the discussion throughout the disclosure. Any standardized test methods pointed to in the examples, disclosure, or claims, unless obvious from the context of their use, refer to a version of the test method publicly available at the time of filing of this disclosure.

[0106] FZG wear is used to evaluate the wear load capacity of a lubricant and is performed according to the A10 / 16.6R / 120 test of ASTM D5182. Results are reported as a breaking load class (FLS), and better results are obtained for samples with higher FLS. Preferably, an FLS of 8 or higher is desired.

[0107] The leaching of copper into the lubricating composition was determined by ICP using a modified procedure according to ASTM D130-19 (using a semi-submerged copper strip heated to approximately 150°C and maintained for approximately 168 hours). Preferably, less than 100 ppm of copper was leached into the fluid after the test.

[0108] The lubricating fluid used in the electric motor was measured using a modified conductivity test according to ASTM D2624-15 at 20 Hz and 100 °C. Preferably, the lubricant exhibited a conductivity of less than 25 nS / M at 100 °C.

[0109] Example 1

[0110] Uncapped succinimide dispersants A through D were prepared and their extreme pressure properties were evaluated. Dispersants A through D are succinimides obtained by reacting polyisobutylene (PIB) with maleic anhydride to form PIB succinic anhydride or acid, and further reacting the PIB succinic anhydride or acid with polyalkylene polyamines, as generally described in US 7,897,696 or US 4,234,435. The dispersants were not further reacted with any post-treatment capping agents. Polyalkylene polyamines are polyamine bottom products (e.g., heavy polyamines) comprising mixtures of polyalkylene polyamines containing small amounts of lower polyamine oligomers (such as TEPA (tetraethylenepentamine) and PEHA (pentaethylenehexamine)) but primarily oligomers with 6 or more nitrogen atoms per molecule, 2 or more primary amines, and more extensive branching than conventional polyamine mixtures. Dispersants C and D comprise polyisobutylene substituents of the dispersant, which are highly reactive PIBs with terminal double bonds of greater than 90 mol%. Table 3 below illustrates samples 2 to 5, each containing approximately 1 wt% of the indicated uncapped dispersant and the same additive package containing the same defoamer, processing oil, amine antioxidant, neutral calcium sulfonate detergent (TBN of approximately 28), ash-free dialkyl dithiophosphate antiwear additive, and blended in an API Group II / III base oil mixture. Sample 1 contains only the additive package blended in an API Group II / III base oil mixture, but no dispersant. FZG wear results are provided in Table 3 below.

[0111] Table 3: Lubricants containing uncapped dispersants

[0112]

[0113] 1. Calculated nitrogen ppm from the dispersant to the fluid.

[0114] 2. Dispersant A is derived from conventional PIB containing less than 10 mol% terminal double bonds of 1000 Mn.

[0115] Dispersant B is derived from 2000 Mn conventional PIB with a terminal double bond content of less than 10 mol%.

[0116] 4. Dispersant C is derived from 1000 Mn highly reactive PIB with terminal double bonds having a content of over 90 mol%.

[0117] 5. Dispersant D is derived from 2300 Mn highly reactive PIB with terminal double bonds having a content of over 90 mol%.

[0118] As shown in Table 3, lubricants containing uncapped dispersants typically have poor FZG performance.

[0119] Example 2

[0120] Various post-treated succinimide dispersants were prepared and their extreme pressure performance, copper leaching performance, and extreme pressure properties were evaluated. The dispersants evaluated for this example included succinimides obtained by reacting PIB with maleic anhydride to form PIB succinic anhydride or acid, and further reacting the PIB succinic anhydride or acid with a polyalkylene polyamine, as described in Example 1 above. A polyalkylene polyamine is a polyamine bottom product (e.g., a heavy polyamine) comprising a mixture of polyalkylene polyamines containing small amounts of lower polyamine oligomers (such as TEPA (tetraethylenepentamine) and PEHA (pentaethylenehexamine)) but primarily oligomers having 6 or more nitrogen atoms per molecule, 2 or more primary amines, and more extensive branching than conventional polyamine mixtures. The succinimide dispersants were then post-treated with various end-capping agents as described below:

[0121] Preparation of Sample A: One equivalent of uncapped dispersant C from Example 1 and 0.3 equivalents of potassium carbonate were fed into a 1L reactor equipped with a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reactor was placed under nitrogen and then heated to approximately 100°C. Then, 0.2 equivalents of benzoyl chloride were added, allowing the reaction to proceed exothermically, and the mixture was maintained at approximately 140°C under vacuum for approximately 2 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter. Potassium carbonate was added at the start of the reaction to neutralize any acidic byproducts (e.g., HCl) that may form with the addition of benzoyl chloride.

[0122] Preparation of Sample B: One equivalent of uncapped dispersant C from Example 1 and one equivalent of potassium carbonate were added to a 1 L reactor equipped with a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reactor was placed under nitrogen and then heated to approximately 100°C. Then, 0.2 equivalents of oleoyl chloride were added, allowing the reaction to proceed exothermically, and the mixture was maintained at approximately 140°C under vacuum for approximately 2 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter. Potassium carbonate was added at the start of the reaction to neutralize any acidic byproducts (e.g., HCl) that may form with the addition of oleoyl chloride.

[0123] Preparation of Sample C: One equivalent of uncapped dispersant C from Example 1 and 0.4 equivalents of potassium carbonate were fed into a 1L reactor equipped with a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reactor was placed under nitrogen and then heated to approximately 100°C. Then, 0.3 equivalents of octyl bromide were added, the reaction was made exothermic, and then maintained at approximately 140°C under vacuum for approximately 2 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter. Potassium carbonate was added at the start of the reaction to neutralize any acidic byproducts (e.g., HBr) that may form with the addition of octyl bromide.

[0124] Preparation of Sample D: One equivalent of uncapped dispersant D from Example 1 and 0.4 equivalents of potassium carbonate were fed into a 1L reactor equipped with a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reactor was placed under nitrogen and then heated to approximately 110°C. Then, 0.3 equivalents of acetic anhydride were added, causing the reaction to be exothermic, and then maintained at approximately 140°C under vacuum for approximately 2 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter. Potassium carbonate was added at the start of the reaction to neutralize any acidic byproducts that might form with the addition of acetic anhydride.

[0125] Preparation of Sample E: One equivalent of uncapped dispersant C from Example 1 and 0.6 equivalents of potassium carbonate were added to a 1 L reactor equipped with a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reactor was placed under nitrogen and then heated to approximately 100°C. Then, 0.4 equivalents of benzyl bromide were added, allowing the reaction to proceed exothermically, and the mixture was maintained at approximately 140°C under vacuum for approximately 2 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter. Potassium carbonate was added at the start of the reaction to neutralize any acidic byproducts (e.g., HBr) that may form with the addition of benzyl bromide.

[0126] Preparation of Sample F: One equivalent of uncapped dispersant C from Example 1 and 0.2 equivalents of cesium carbonate were fed into a 1L reactor equipped with a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reactor was placed under nitrogen and then heated to approximately 110°C. Then, 0.2 equivalents of ethylene carbonate were added, and the reaction was made exothermic, and then maintained at approximately 160°C under vacuum for approximately 3 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter.

[0127] Preparation of Sample G: One equivalent of uncapped dispersant C from Example 1 was fed into a 1L reactor equipped with a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reactor was placed under nitrogen and then heated to approximately 100°C. Then, 0.2 equivalents of phenyl isocyanate were added, and the reaction was made exothermic, then maintained under vacuum at approximately 140°C for approximately 2 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter.

[0128] Preparation of Sample H: One equivalent of uncapped dispersant C from Example 1, 0.2 equivalents of 2-ethylhexyl glycidyl ether, and 0.1 equivalents of pyridine were fed into a 1 L reactor equipped with a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reaction was stirred at 105°C for 20 hours, and then water was added under vacuum and the mixture was heated to 120°C to vaporize the pyridine from the product. The reactor was then kept heated under vacuum at approximately 145°C for approximately 2 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter.

[0129] Preparation of Sample I: One equivalent of uncapped dispersant A from Example 1 and 0.4 equivalents of potassium carbonate were fed into a 1L reactor equipped with a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reactor was placed under nitrogen and then heated to approximately 110°C. Then, 0.3 equivalents of acetic anhydride were added, causing the reaction to be exothermic, and then maintained at approximately 140°C under vacuum for approximately 2 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter. Potassium carbonate was added at the start of the reaction to neutralize any acidic byproducts that might form with the addition of acetic anhydride.

[0130] Preparation of Sample J: Eschweiler-Clark methylation was performed by adding 1 equivalent of uncapped dispersant C from Example 1 to a 1 L reactor, followed by the addition of 0.3 equivalents of 37% formaldehyde (aqueous solution) using a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reactor was placed under nitrogen protection and heated to approximately 80°C with stirring for 6 hours. Then, 0.5 equivalents of formic acid were added dropwise over 2 hours with stirring overnight for 18 hours. A vacuum was then applied at 140°C for 2 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter.

[0131] Preparation of Sample K: One equivalent of uncapped dispersant C from Example 1 was fed into a 1 L reactor equipped with a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reactor was placed under nitrogen and then heated to approximately 110°C. Then, 0.2 equivalents of indocyanine anhydride were added, causing the reaction to be exothermic, and the mixture was then held under vacuum at approximately 140°C for approximately 2 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter.

[0132] Preparation of Sample L: One equivalent of uncapped dispersant C from Example 1 and 0.4 equivalents of potassium carbonate were fed into a 1L reactor equipped with a stirrer, thermocouple, heating mantle, and Dean-Stark water separator. The reactor was placed under nitrogen and then heated to approximately 110°C. Then, 0.3 equivalents of acetic anhydride were added, the reaction was made exothermic, and then maintained at approximately 140°C under vacuum for approximately 2 hours. The resulting product was filtered under pressure through a Hiflow Super Cel Celite filter. Potassium carbonate was added at the start of the reaction to neutralize any acidic byproducts that might form with the addition of acetic anhydride.

[0133] Table 4: Dispersants for End Capping

[0134]

[0135] Total nitrogen in dispersants (ASTM D5291)

[0136] Example 3

[0137] Approximately 1% by weight of the various end-capping dispersants from Example 2 were added to the additive package and blended with an API Group II / III base oil mixture to form an electric motor lubricating fluid suitable for electric or hybrid electric vehicles. The additive package was identical in each sample and contained an ash-free dialkyl dithiophosphate anti-wear additive comprising at least 3-[[bis(2-methylpropoxy)phosphothio]thio]-2-methylpropionic acid, an antifoaming agent, a processing oil, an amine antioxidant, and a low-alkaline calcium sulfonate detergent (with approximately 28 TBN). The additive package was present in an amount delivering approximately 60 ppm phosphorus and approximately 120 ppm sulfur from the anti-wear additive to the fluid. The low-alkaline calcium sulfonate detergent was present in an amount delivering approximately 36 ppm calcium to the fluid. Extreme pressure, copper leaching, and conductivity results are provided in Table 5 below.

[0138] Table 5: Lubrication Performance

[0139]

[0140] As shown in Table 5 above, while comparative lubricants C1, C2, C4, C5, and C6 exhibited low conductivity below 25 nS / M, these comparative lubricants had low FLS ratings and / or high copper leaching, and were otherwise unacceptable as lubricating fluids for electric motors. Comparative lubricants C3 and C7 had unacceptably high conductivity. The lubricant of the present invention has the same composition as the comparative lubricants, except for the dispersant with different end-capping agents, and unexpectedly, the lubricant of the present invention achieves low conductivity (e.g., less than 25 nS / M at 100°C), low copper leaching (e.g., less than 100 ppm of copper), and a high FLS rating (e.g., at least 8 FLS). It is not expected that changing the end-capping agent on the dispersant compound would affect all three performance evaluations.

[0141] It should be understood that although the lubricating compositions and formulations of this disclosure have been described in conjunction with their detailed description and summary herein, the foregoing description is intended to be illustrative and not limiting of the scope of this disclosure, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are also within the scope of the claims. This specification and the examples are intended to be illustrative only, wherein the true scope of this disclosure is indicated by the appended claims.

[0142] Other embodiments of this disclosure will be apparent to those skilled in the art upon consideration of the practice of this specification and the embodiments disclosed herein. As used throughout the specification and claims, “a / an (a)” and / or “an / an (a)” may refer to one or more. Unless otherwise indicated, all figures expressing quantities of components and properties, such as molecular weight, percentage, ratio, reaction conditions, etc., used in this specification should be understood to be modified in all cases by the term “about,” regardless of whether the term “about” is present. Therefore, unless indicated to the contrary, the numerical parameters set forth in this specification are approximations that may vary depending on the desired properties sought to be obtained through this disclosure. To a minimum, and without attempting to limit the application of the equivalence principle to the scope of the claims, each numerical parameter should be interpreted at least according to the number of significant figures reported and by applying general rounding techniques. Although the numerical ranges and parameters set forth in the broad scope of this disclosure are approximations, the values ​​set forth in particular embodiments are reported as precisely as possible. However, any numerical value inherently contains some error necessarily caused by the standard deviation found in its corresponding test measurement.

[0143] It should be understood that each component, compound, substituent or parameter disclosed herein should be interpreted as disclosed for use alone or in combination with one or more of each other component, compound, substituent or parameter disclosed herein.

[0144] It should also be understood that each range disclosed herein should be interpreted as a disclosure of each specific value within the disclosed range having the same significant digits. Thus, the range 1 to 4 will be interpreted as an explicit disclosure of the values ​​1, 2, 3, and 4, and any range of these values, such as 1 to 4, 1 to 3, 1 to 2, 2 to 4, 2 to 3, and so on.

[0145] It should also be understood that each lower limit of each range disclosed herein should be interpreted as a combination of each upper limit of each range and each specific value within each range disclosed herein for the same component, compound, substituent, or parameter. Therefore, this disclosure should be interpreted as a disclosure of all ranges derived by combining each lower limit of each range with each upper limit of each range or with each specific value within each range, or by combining each upper limit of each range with each specific value within each range.

[0146] Furthermore, the specific amounts / values ​​of components, compounds, substituents, or parameters disclosed in this specification or examples should be interpreted as disclosures of a lower or upper limit of a range, and therefore can be combined with any other lower or upper limit or specific amount / value of the range of the same components, compounds, substituents, or parameters disclosed elsewhere in this disclosure to form such a range of components, compounds, substituents, or parameters.

Claims

1. A lubricating fluid for an electric motor in an electric or hybrid electric vehicle, the electric motor lubricating fluid comprising: One or more base oils with lubricating viscosity; An oil-soluble phosphorus anti-wear additive comprising ash-free dialkyl dithiophosphoric acid, wherein the oil-soluble phosphorus anti-wear additive provides the electric motor lubricating fluid with no more than about 200 ppm of sulfur; The succinimide dispersant reaction product is obtained through the following steps: (i) A dicarboxylic acid or anhydride with a hydrocarbon-substituted group is reacted with a polyalkylene polyamine to form an intermediate having at least one secondary amine. (ii) Reacting the secondary amine with a capping agent, the capping agent comprising one or more of C6 or higher alkyl halides, acetic anhydride and / or phenyl isocyanate; The electric motor lubricating fluid contains less than about 300 ppm of total sulfur; and The electric motor lubricating fluid described herein contains virtually no corrosion inhibitor additives.

2. The electric motor lubricating fluid of claim 1, wherein the electric motor lubricating fluid is substantially free of boron; and / or wherein the electric motor lubricating fluid further comprises up to about 0.8% by weight of one or more amine antioxidant nitrogen; and / or wherein the electric motor lubricating fluid is substantially free of corrosion inhibitor additives selected from substituted or unsubstituted benzotriazole or triazole compounds, tolyltriazole compounds, corrosion inhibitors derived from monocarboxylic or polycarboxylic acids, alkenyl succinic acid or acid anhydride corrosion inhibitors, corrosion inhibitors derived from ether amines, acid phosphates, polyethoxylated compounds, imidazolines, or combinations thereof.

3. The electric motor lubricating fluid of claim 1, further comprising a sulfonate detergent, the amount of which contributes about 3 to about 50 TBN (ASTM D2896) to the electric motor lubricating fluid; and / or wherein the sulfonate detergent is preferably calcium sulfonate, and provides about 10 ppm to about 250 ppm of calcium to the electric motor lubricating fluid.

4. The electric motor lubricating fluid of claim 1, wherein the oil-soluble phosphorus anti-wear additive comprising ashless dialkyl dithiophosphate is prepared by a method comprising the steps of: (a) reacting an organic hydroxy compound with phosphorus pentasulfide to form a reaction product, and (b) further reacting the reaction product with an unsaturated carboxylic acid to form the oil-soluble phosphorus anti-wear additive comprising the ashless dialkyl dithiophosphate.

5. The electric motor lubricating fluid according to claim 1, wherein the ashless dialkyl dithiophosphate comprises a compound of formula I or a salt thereof: (Form IIa) R4 and R5 are independently C1 to C1. 10 A straight-chain or branched alkyl group, and R6 is -H or -CH3.

6. The electric motor lubricating fluid according to claim 5, wherein the ashless dialkyl dithiophosphate comprises 3-[[bis(2-methylpropoxy)thiophosphono]thio]-2-methylpropionic acid.

7. The electric motor lubricating fluid according to claim 1, wherein the succinimide dispersant is post-treated with a capping agent that is substantially free of phosphorus compounds and / or substantially free of boron compounds.

8. The electric motor lubricating fluid of claim 1, wherein the electric motor lubricating fluid exhibits copper leaching of about 100 ppm or less according to ASTM D130; and wherein the electric motor lubricating fluid has a destructive load class of 8 or higher in the FZG A10 / 16.6R / 120 test of ASTM D5182; and wherein the electric motor lubricating fluid exhibits a conductivity of less than 25 nS / M at 100°C, measured using the electric motor lubricating fluid and measured at 20 Hz and 100°C, according to a modified conductivity test according to ASTM D2624-15.

9. A method for lubricating a power transmission system component including an electric motor, the method comprising: The power transmission system components are lubricated with an electric motor lubricating fluid, wherein the electric motor lubricating fluid contacts a portion of the electric motor; The electric motor lubricating fluid comprises: (a) one or more base oils having a lubricating viscosity; (b) an oil-soluble phosphorus anti-wear additive comprising ash-free dialkyl dithiophosphate, the oil-soluble phosphorus anti-wear additive providing the electric motor lubricating fluid with no more than about 200 ppm of sulfur; (c) a succinimide dispersant reaction product obtained by the following steps: (i) reacting a hydrocarbon-substituted dicarboxylic acid or anhydride with a polyalkylene polyamine to form an intermediate having at least one secondary amine, and (ii) reacting the secondary amine with a capping agent comprising one or more of C6 or higher alkyl halides, acetic anhydride, and / or phenyl isocyanate; and (d) wherein the electric motor lubricating fluid contains less than about 300 ppm of total sulfur; and The electric motor lubricating fluid described therein exhibits: approximately 100 ppm or less of copper leaching according to ASTM D130; a destructive load class of 8 or higher in the FZG A10 / 16.6R / 120 test according to ASTM D5182; and / or a conductivity of less than 25 nS / M at 100°C, measured using the electric motor lubricating fluid and measured at 20 Hz and 100°C, according to a modified conductivity test according to ASTM D2624-15.

10. The method of claim 9, wherein the electric motor lubricating fluid is substantially free of boron.

11. The method of claim 9, further comprising a sulfonate detergent, the amount of which contributes about 3 to about 50 TBN (ASTM D2896) to the electric motor lubricating fluid; and wherein the sulfonate detergent is calcium sulfonate, and the sulfonate detergent provides about 10 ppm to about 250 ppm of calcium to the electric motor lubricating fluid.

12. The method of claim 9 further comprises up to about 0.8% by weight of one or more amine antioxidants.

13. The method of claim 9, wherein the electric motor lubricating fluid is substantially free of corrosion inhibitor additives, the corrosion inhibitor additives being selected from substituted or unsubstituted benzotriazole or triazole compounds, toluenetriazole compounds, corrosion inhibitors derived from monocarboxylic or polycarboxylic acids, alkenyl succinic acid or acid anhydride corrosion inhibitors, corrosion inhibitors derived from ether amines, acid phosphates, polyethoxylated compounds, imidazolines, or combinations thereof.

14. The method of claim 9, wherein the oil-soluble phosphorus anti-wear additive comprising the ashless dialkyl dithiophosphate is prepared by a method comprising the steps of: (a) reacting an organic hydroxyl compound with phosphorus pentasulfide to form a reaction product, and (b) further reacting the reaction product with an unsaturated carboxylic acid to form the oil-soluble phosphorus anti-wear additive comprising the ashless dialkyl dithiophosphate; and / or wherein the ashless dialkyl dithiophosphate comprises a compound of formula I or a salt thereof: (Form IIa) R4 and R5 are independently C1 to C1. 10 A straight-chain or branched alkyl group, and R6 is -H or -CH3.

15. The method of claim 9, wherein the succinimide dispersant is post-treated with a capping agent that is substantially free of phosphorus-containing compounds and / or substantially free of boron-containing compounds.

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