Low-viscosity lubricating fluid for an electric motor system

Abstract

An electric motor lubricating fluid for an electric motor system, the electric motor lubricating fluid comprising a lubricating base oil, at least one sulfurized component, at least two phosphorus-containing additives, and at least one high molecular weight dispersant. The electric motor lubricating fluid provides acceptable wear performance as well as good electrical conductivity and oxidation stability for use in an electric motor system fluid having a low viscosity.

Description

TECHNICAL FIELD

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

[0002] The main challenges in developing lubricants for electric vehicle powertrains are to achieve acceptable anti-wear and friction performance and maintain oxidative stability while ensuring compatibility of the lubricant with the energized components in the powertrain. Since 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 also needs to be relatively low to inhibit electrostatic accumulation and discharge of the energized components.

[0003] To improve efficiency, lubricant manufacturers often seek lower lubricant viscosities, but lower viscosity fluids are often less desirable for the demanding wear and friction tests often required by industrial and / or automotive manufacturers. Thus, low viscosity fluids may typically require additional anti-wear additives to meet the required wear tests. However, adding these additional additives generally increases the electrical conductivity and reduces the oxidative stability of the lubricant. For example, a lubricant having a kinematic viscosity at 100 °C (ASTM D445) of about 4.5 cSt or less may require a higher amount of anti-wear additive than is required in a higher viscosity lubricant to achieve the required anti-wear performance, but the addition of certain anti-wear additives may result in an increase in electrical conductivity and a decrease in oxidative stability. In particular, it has been challenging for low-viscosity lubricants having a kinematic viscosity at 100 °C of about 4.5 cSt or less, or 3.5 cSt or less, or 3.0 cSt or less to pass a demanding FZG wear test (such as the demanding A10 / 16.6R / 90 scuffing test of CEC L-84-02), while also exhibiting low electrical conductivity and maintaining oxidative stability. SUMMARY OF THE INVENTION

[0004] In one embodiment, an electric motor lubricating fluid suitable for an electric or hybrid electric vehicle is described herein. In various methods, the electric motor lubricating fluid comprises: one or more base oils having a lubricating viscosity; a succinimide dispersant derived from a polyisobutylene having a number average molecular weight of about 2,000 or greater, wherein the succinimide dispersant has about 0.5 wt% to about 1 wt% nitrogen and is post-treated with a phosphorus-containing compound and a boron-containing compound, and wherein the succinimide dispersant delivers about 70 ppm to about 140 ppm of phosphorus and about 150 ppm to about 300 ppm of nitrogen to the electric motor lubricating fluid; an amine salt of a phosphate ester that provides about 40 ppm to about 70 ppm of phosphorus to the electric motor lubricating fluid; an oil-soluble phosphorus antiwear additive comprising ashless dialkyldithiophosphate that provides about 40 ppm to about 70 ppm of phosphorus to the electric motor lubricating fluid; a sulfur donating additive comprising thiadiazole or a derivative thereof that provides up to about 950 ppm of sulfur to the electric motor lubricating fluid; and wherein the electric motor lubricating fluid has a kinematic viscosity at 100 °C of about 4.5 cSt or less and a total phosphorus of about 150 ppm to about 250 ppm.

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

[0006]

[0007] wherein R 1 and R 2 are independently hydrogen or a straight-chain, branched-chain or cyclic hydrocarbon group; m is an integer from 0 to 1, p is an integer from 1 to 2, and m + p equals 2; R 3 , R 4 , R 5 and R 6 are independently hydrogen or a hydrocarbon group, and at least one of R 3 to R 6 is a hydrocarbon group; and / or wherein R 1 and R 2 are independently C 3 to C 10 alkyl groups, and at least one of R 3 , R 4 , R 5 and R 6 is a C 10 to C 20an alkyl group; and / or the number average molecular weight of the high molecular weight polyisobutene is from about 2,000 to about 2,300; and / or wherein the electric motor lubricating fluid comprises from about 2 wt% to about 4 wt% of a succinimide dispersant; and / or wherein the succinimide dispersant, the amine salt of a phosphate ester, the ashless dialkyldithiophosphate, and the thiadiazole or its derivative are provided in an additive concentrate, and wherein the additive concentrate has a kinematic viscosity (kV) at 100 °C of from about 15 cSt to about 80 cSt; and / or wherein the ratio of the kV100 °C of the additive concentrate to the kV100 °C of the electric motor lubricating fluid is from about 5:1 to about 30:1; and / or after aging, the change in viscosity of the electric motor lubricating fluid is less than 0.09 cSt according to CEC L-48-A); and / or wherein the electric motor lubricating fluid achieves at least a failure load stage of 8 in the FZG A10 / 16.6R / 90 scuffing resistance test of CEC L-84-02; and / or wherein the electric motor lubricating fluid has a conductivity of about 60 nS / M or less, as measured by a modified conductivity test of the electric motor lubricating fluid according to ASTM D2624-15 and measured at 20 Hz and 100 °C; and / or the oil-soluble phosphorus antiwear additive comprising an ashless dialkyldithiophosphate is prepared by a method comprising the steps of: (a) reacting an organic hydroxy compound with phosphorus pentasulfide to form a reaction product, and further reacting the reaction product with an unsaturated carboxylic acid to form an oil-soluble phosphorus antiwear additive comprising an ashless dialkyldithiophosphate; and / or wherein the ashless dialkyldithiophosphate comprises a compound of formula II or its salt:

[0008]

[0009] wherein R 7 and R 8 are independently C 3 to C 8 linear or branched alkyl groups, and R 9 is -H or -CH 3 ; and / or wherein the ashless dialkyldithiophosphate is 3-[[bis(2-methylpropoxy)thiophosphinyl]thio]-2-methylpropanoic acid; and / or wherein the thiadiazole or its derivative comprises one or more compounds having the structure of formula III:

[0010]

[0011] wherein each R 10 is independently hydrogen or sulfur; each R 11 is independently an alkyl group; n is an integer of 0 or 1, and if R 10 is hydrogen, then adjacent R 11The integer n of the moiety is 0, and if R 10 is sulfur, then the n of the adjacent R 11 moiety is 1; and at least one of the Rs 10 is sulfur; and / or the electric motor lubricating fluid further comprises one or more metal-containing detergent additives that provide no more than about 50 ppm of calcium to the electric motor lubricating fluid.

[0012] In other embodiments, the present disclosure provides an additive concentrate suitable for an electric motor lubricating fluid. In each method, the additive concentrate comprises: a succinimide dispersant derived from a high molecular weight polyisobutylene having a number average molecular weight of about 2,000 or greater, wherein the succinimide dispersant has about 0.5 wt% to about 1 wt% nitrogen and is post-treated with a phosphorus-containing compound and a boron-containing compound, and wherein the succinimide dispersant is present in an amount that delivers about 1400 ppm to about 2450 ppm of phosphorus and about 3000 ppm to about 5400 ppm of nitrogen to the dispersant additive concentrate; an amine salt of a phosphate ester that provides about 1000 ppm to about 1500 ppm of phosphorus to the additive concentrate; an oil-soluble phosphorus antiwear additive comprising ashless dialkyldithiophosphate that provides about 800 ppm to about 1300 ppm of phosphorus to the additive concentrate; a sulfur donor additive comprising a thiadiazole or a derivative thereof that provides sulfur to the additive concentrate but no more than about 18,000 ppm of sulfur; and wherein the additive concentrate has a kinematic viscosity at 100 °C of about 15 cSt to about 80 cSt.

[0013] In other embodiments, the additive concentrate of the previous paragraph may include one or more optional features or embodiments in any combination. These optional features or embodiments may include one or more of the following: wherein the amine salt of the phosphate ester has the structure of Formula I or a solvate or hydrate thereof:

[0014]

[0015] wherein R 1 and R 2 are independently hydrogen or a linear, branched or cyclic hydrocarbon group; m is an integer from 0 to 1, p is an integer from 1 to 2, and m + p equals 2; R 3 , R 4 , R 5 and R 6 are independently hydrogen or a hydrocarbon group, and at least one of R 3 to R 6 is a hydrocarbon group; and / or wherein R 1 and R 2 are independently C3 to C10 alkyl groups, and wherein R3 , R 4 , R 5 and R 6 at least one of which is a C 10 to C 20 alkyl group; and / or the number average molecular weight of the high molecular weight polyisobutene is from about 2,000 to about 2,300; and / or wherein the succinimide dispersant accounts for about 40 wt% to about 70 wt% of the additive concentrate; and / or the oil-soluble phosphorus antiwear additive comprising ashless dialkyldithiophosphate is prepared by a process comprising the steps of: (a) reacting an organic hydroxy compound with phosphorus pentasulfide to form a reaction product, and further reacting the reaction product with an unsaturated carboxylic acid to form an oil-soluble phosphorus antiwear additive comprising ashless dialkyldithiophosphate; and / or wherein the ashless dialkyldithiophosphate comprises a compound of formula II or a salt thereof:

[0016]

[0017] wherein R 7 and R 8 are independently C 3 to C 8 linear or branched alkyl groups, and R 9 is -H or -CH 3 ; and / or wherein the ashless dialkyldithiophosphate is 3-[[bis(2-methylpropoxy)thiophosphinyl]thio]-2-methylpropanoic acid; and / or wherein the thiadiazole or its derivative comprises one or more compounds having the structure of formula III:

[0018]

[0019] wherein each R 10 is independently hydrogen or sulfur; each R 11 is independently an alkyl group; n is an integer of 0 or 1, and if R 10 is hydrogen, the integer n of the adjacent R 11 portion is 0, and if R 10 is sulfur, the n of the adjacent R 11 portion is 1; and wherein at least one R 10 is sulfur; and / or the additive concentrate further comprises one or more metal-containing detergent additives providing no more than about 950 ppm of calcium to the additive concentrate.

[0020] In other embodiments, a method for lubricating powertrain components including an electric motor is also described herein. In each method, the method includes lubricating the powertrain components with an electric motor lubricating composition, and wherein the electric motor lubricating composition contacts portions of the electric motor; and wherein the electric motor lubricating composition comprises: (i) one or more base oils having lubricating viscosity; (ii) a succinimide dispersant derived from a high molecular weight polyisobutene having a number average molecular weight of about 2,000 or greater, wherein the succinimide dispersant has about 0.5 wt% to about 1 wt% nitrogen and is post-treated with a phosphorus-containing compound and a boron-containing compound, and wherein the succinimide dispersant delivers about 70 ppm to about 140 ppm of phosphorus and about 150 ppm to about 300 ppm of nitrogen to the electric motor lubricating fluid; (iii) an amine salt of a phosphate ester that provides about 40 ppm to about 70 ppm of phosphorus to the electric motor lubricating fluid; (iv) an oil-soluble phosphorus antiwear additive including ashless dialkyldithiophosphate that provides about 40 ppm to about 70 ppm of phosphorus to the electric motor lubricating fluid; and (v) a sulfur donating additive including thiadiazole or a derivative thereof that provides sulfur to the electric motor lubricating fluid but not more than about 950 ppm of sulfur; and wherein the electric motor lubricating fluid has a kV100°C of about 4.5 cSt or less, a total phosphorus of about 150 ppm to about 250 ppm, and a conductivity of about 37 nS / M or less, as measured by a modified conductivity test of the electric motor lubricating fluid according to ASTM D2624-15 and measured at 20 Hz and 100°C.

[0021] In additional embodiments, the method for lubricating powertrain components including an electric motor of the previous paragraph may further 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 amine salt of the phosphate ester has the structure of Formula I or a solvate or hydrate thereof:

[0022]

[0023] wherein R 1 and R 2 are independently hydrogen or a straight-chain, branched-chain, or cyclic hydrocarbon group; m is an integer from 0 to 1, p is an integer from 1 to 2, and m + p equals 2; R 3 , R 4 , R 5 and R 6 are independently hydrogen or a hydrocarbon group, and at least one of R 3 to R 6 is a hydrocarbon group; and / or wherein R1 and R 2 are independently C 3 to C 10 alkyl groups, and wherein R 3 , R 4 , R 5 and R 6 at least one of which is C 10 to C 20 alkyl group; and / or the number average molecular weight of the high molecular weight polyisobutene is from about 2,000 to about 2,300; and / or wherein the electric motor lubricating fluid comprises from about 2 wt% to about 4 wt% of a succinimide dispersant; and / or wherein the succinimide dispersant, amine salt of phosphoric acid ester, oil-soluble phosphorus antiwear additive comprising ashless dialkyldithiophosphate, and sulfur donating additive comprising thiadiazole or its derivatives are provided in an additive concentrate having a kinematic viscosity (kV) at 100 °C of from about 15 cSt to about 80 cSt; and / or wherein the ratio of the kV100 °C of the additive concentrate to the kV100 °C of the electric motor lubricating fluid is from about 5:1 to about 30:1; and / or the electric motor lubricating fluid, after aging, has a viscosity change of less than 0.09 cSt according to CEC L-48-A; and / or wherein the electric motor lubricating fluid achieves at least a failure load stage of 8 in the FZG A10 / 16.6R / 90 scuffing resistance test of CEC L-84-02; and / or the oil-soluble phosphorus antiwear additive comprising ashless dialkyldithiophosphate is prepared by a method comprising the steps of: (a) reacting an organic hydroxy compound with phosphorus pentasulfide to form a reaction product, and further reacting the reaction product with an unsaturated carboxylic acid to form an oil-soluble phosphorus antiwear additive comprising ashless dialkyldithiophosphate; and / or wherein the ashless dialkyldithiophosphate comprises a compound of formula II or its salt:

[0024]

[0025] wherein R 7 and R 8 are independently C3 to C8 straight-chain or branched-chain alkyl groups, and R 9 is -H or -CH 3 ; and / or wherein the ashless dialkyldithiophosphate is 3-[[bis(2-methylpropoxy)thiophosphinyl]thio]-2-methylpropanoic acid; and / or wherein the thiadiazole or its derivatives comprise one or more compounds having a structure of formula III:

[0026]

[0027] wherein each R 10 is independently hydrogen or sulfur; each R 11independently an alkyl group; n is an integer of 0 or 1, and if R 10 is hydrogen, the integer n of the adjacent R 11 moiety is 0, and if R 10 is sulfur, the n of the adjacent R 11 moiety is 1; and wherein at least one R 10 is sulfur; and / or wherein the electric motor lubricating composition further comprises one or more metal-containing detergent additives that provide no more than about 50 ppm of calcium to the electric motor lubricating composition.

[0028] In a further embodiment, the present disclosure provides the use of an additive concentrate in an electric motor lubricating composition and / or the use of an electric motor lubricating composition for achieving a kV100 °C of about 4.5 cSt or less, the electric motor lubricating composition having a total phosphorus of about 150 ppm to about 250 ppm and an electrical conductivity of about 37 nS / M or less, as measured by a modified conductivity test of the electric motor lubricating fluid according to ASTM D2624-15 and measured at 20 Hz and 100 °C. In other embodiments, the use includes an electric motor lubricating composition comprising: (i) one or more base oils having lubricating viscosity; (ii) a succinimide dispersant derived from a high molecular weight polyisobutylene having a number average molecular weight of about 2,000 or greater, wherein the succinimide dispersant has about 0.5 wt% to about 1 wt% nitrogen and is post-treated with a phosphorus-containing compound and a boron-containing compound, and wherein the succinimide dispersant delivers about 70 ppm to about 140 ppm of phosphorus and about 150 ppm to about 300 ppm of nitrogen to the electric motor lubricating fluid; (iii) an amine salt of a phosphate ester that provides about 40 ppm to about 70 ppm of phosphorus to the electric motor lubricating fluid; (iv) an oil-soluble phosphorus antiwear additive comprising ashless dialkyldithiophosphate that provides about 40 ppm to about 70 ppm of phosphorus to the electric motor lubricating fluid; and (v) a sulfur donor additive comprising thiadiazole or a derivative thereof that provides sulfur to the electric motor lubricating fluid but not more than about 950 ppm of sulfur. In other methods or embodiments, the use may further include any other embodiment of the electric motor lubricating composition, any other embodiment of the method, or any other embodiment of the additive concentrate as described above in the present disclosure.

[0029] 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.

[0030] The following term definitions are provided to clarify the meaning of certain terms as used herein.

[0031] The terms "lubricating oil", "lubricant composition", "lubricating composition", "lubricant", and "lubricating and cooling fluid" refer to finished lubricating products containing a major amount of base oil and a minor amount of an additive composition.

[0032] As used herein, the terms "additive package", "additive concentrate", and "additive composition" refer to the portion of a lubricating oil composition that does not include a major amount of base oil.

[0033] 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 connected to the remainder of the molecule and predominantly having hydrocarbon character. Each hydrocarbyl group is independently selected from hydrocarbon substituents and substituted hydrocarbon substituents containing one or more halogen groups, hydroxy groups, alkoxy groups, mercapto groups, nitro groups, nitroso groups, amino groups, pyridyl groups, furyl groups, imidazolyl groups, oxygen, and nitrogen, and wherein there are no more than two non-hydrocarbon substituents for every ten carbon atoms in the hydrocarbyl group.

[0034] As used herein, unless otherwise expressly stated, the term "weight percent" or "wt%" means the percentage by weight of the component in the entire composition.

[0035] The terms "soluble", "oil-soluble", or "dispersible" as used herein may but do not necessarily mean that the compound or additive is soluble, dissolvable, miscible, or capable of being suspended in oil in all proportions. However, the foregoing terms do mean that they are, for example, soluble, suspendable, dissolvable, or stably dispersible in oil to an extent sufficient to perform their intended function in an environment employing the oil. Additionally, if desired, the incorporation of other additives may also permit the incorporation of higher levels of a particular additive.

[0036] As used herein, the term "alkyl" refers to a straight-chain, branched-chain, cyclic, and / or substituted saturated chain moiety of from about 1 to about 200 carbon atoms.

[0037] As used herein, the term "alkenyl" refers to a straight-chain, branched-chain, cyclic, and / or substituted unsaturated chain moiety of from about 3 to about 30 carbon atoms.

[0038] As used herein, the term "aryl" refers to monocyclic and polycyclic aromatic compounds, which may include alkyl, alkenyl, alkylaryl, amino, hydroxy, alkoxy, halogen substituents, and / or heteroatoms including but not limited to nitrogen and oxygen.

[0039] As used herein, the "number average molecular weight" or "Mn" is determined by gel permeation chromatography (GPC) using commercially available polystyrene standards (wherein Mn is from about 180 to about 18,000 as a calibration reference).

[0040] It should be understood that throughout this disclosure, the terms "comprising," "including," "containing," etc. are considered to be open-ended and include any element, step, or ingredient not explicitly listed. The phrase "consisting essentially of" means including any explicitly listed element, step, or ingredient and any additional element, step, or ingredient that does not materially affect the basic and novel aspects of the invention. This disclosure also contemplates that any composition described using the terms "comprising," "including," "containing" is also interpreted to include the disclosure of the same composition "consisting essentially of its specifically listed components" or "consisting of its specifically listed components." Detailed Description

[0041] According to an exemplary embodiment, an electric motor lubricating fluid suitable for an electric or hybrid electric vehicle is described herein. The electric motor lubricating fluid has a low kinematic viscosity at 100 °C (kV100°C) of about 4.5 cSt or less, about 3.5 cSt or less, or about 3.0 cSt or less, and is still able to pass a severe FZG scuffing test (such as the A10 / 16.6R / 90 test of CEC L-84-02), and at the same time achieve good electrical conductivity and maintain oxidation stability. However, surprisingly with respect to the lubricating fluids herein, it has been found that a combination of certain additives (including succinimide dispersants derived from relatively high molecular weight polyisobutene) helps to achieve passing the wear, conductivity, and oxidation performance tests. When the selected relatively high molecular weight dispersants described herein are incorporated into an additive concentrate, an additive concentrate with a relatively high viscosity is produced. Such high viscosity additive concentrates have not previously been used in low viscosity finished lubricants (such as finished lubricants having a kV100°C of about 4.5 cSt or less, about 3.5 cSt or less, or about 3.0 cSt or less) that require strict wear protection, low electrical conductivity, and oxidation stability.

[0042] It was not expected that a relatively high viscosity additive concentrate having a relatively high molecular weight succinimide dispersant would be suitable for forming a low viscosity finished lubricant capable of passing the wear, conductivity, and oxidation performance tests of an electric and / or hybrid electric vehicle. However, when the selected relatively high molecular weight succinimide dispersants herein are mixed with other lubricant additives having certain elemental relationships to form a finished lubricant, the finished lubricants herein achieve low viscosity, passing wear performance, suitable electrical conductivity, and oxidation stability for a powertrain having an electric or hybrid electric motor.

[0043] It has been found herein that if such high molecular weight dispersants are also provided in combination in the finished fluid in an amount with a selected amount of phosphorus, nitrogen, and / or sulfur from other additives (including, for example, amine salts of phosphate esters, ashless dialkyldithiophosphates, and thiadiazoles or their derivatives), a relatively high molecular weight polyisobutene dispersant can be provided to a fluid for such electric or hybrid-electric applications having a low finished fluid viscosity. In one method, for example, the fluid herein includes: (i) a succinimide dispersant derived from a polyisobutene having a number average molecular weight of about 2,000 or greater and having up to 1 wt% nitrogen, post-treated with a phosphorus-containing compound and a boron-containing compound, and wherein the succinimide dispersant delivers from about 60 ppm to about 120 ppm of phosphorus and from about 150 ppm to about 300 ppm of nitrogen to an electric motor lubricating fluid; (ii) an amine salt of a phosphate ester that provides from about 45 ppm to about 75 ppm of phosphorus to the electric motor lubricating fluid; (iii) an oil-soluble phosphorus antiwear additive including an ashless dialkyldithiophosphate that provides from about 40 ppm to about 70 ppm of phosphorus to the electric motor lubricating fluid; (iv) a sulfur-supplying additive including a thiadiazole or its derivative that supplies no more than sulfur but provides no more than about 950 ppm of sulfur to the electric motor lubricating fluid; and wherein the electric motor lubricating fluid has a kV100°C (ASTM D4450) of about 4.5 cSt or less, about 3.5 cSt or less, or about 3.0 cSt or less, a total phosphorus of from about 150 ppm to about 250 ppm, and a conductivity of about 60 nS / M or less, as measured by a modified conductivity test according to ASTM D2624-15 using the electric motor lubricating fluid and measured at about 20 Hz and about 100°C. In other embodiments, the lubricants herein may also contain an amount of calcium from a detergent additive (such as up to about 50 ppm of calcium in the lubricant or up to about 950 ppm of calcium in an additive concentrate from a neutral to low-alkaline detergent). Each of the component additives is further described below.

[0044] Succinimide dispersant:

[0045] The lubricating fluid for an electric motor of the present disclosure contains a dispersant system including at least one oil-soluble ashless dispersant, which is a succinimide dispersant derived from a relatively high molecular weight polyisobutylene having a number average molecular weight of about 2,000 or greater, and is post-treated with a phosphorus-containing compound and a boron-containing compound. At a suitable treatment rate, such relatively high molecular weight succinimide dispersants produce a dispersant additive concentrate having a kinematic viscosity (kV100°C (ASTM D445)) of about 15 cSt to about 80 cSt. The succinimide dispersants of the present disclosure can be derived from relatively high molecular weight hydrocarbyl-substituted dicarboxylic acids or acid anhydrides reacted with polyalkylene polyamines. The succinimide dispersants and their preparation are disclosed in US 7,897,696 and / or US 4,234,435, which are incorporated herein by reference.

[0046] The relatively high molecular weight hydrocarbyl moiety of the hydrocarbyl dicarboxylic acid or acid anhydride can be derived from a butene polymer, such as a polymer of isobutylene. Suitable polyisobutenes for use herein include those formed from conventional polyisobutenes or highly reactive polyisobutenes having an end vinylidene content of at least 60%, such as 70% to 90% and higher. Suitable polyisobutenes can include those prepared using BF 3 catalysts.

[0047] The dispersants of the present disclosure have a relatively high molecular weight. Thus, the number average molecular weight of the polyisobutylene substituents of the dispersants of the present disclosure can vary from at least about 2,000, and in some cases, up to about 3,000, as measured by gel permeation chromatography (GPC) using polystyrene (having a number average molecular weight of 180 to about 18,000) as a calibration reference. The GPC method also provides average weight molecular weight distribution information; see, for example, W.W. Yau, J.J. Kirkland, and D.D. Bly, “Modern Size Exclusion Liquid Chromatography”, John Wiley and Sons, New York, 1979, which is also incorporated herein by reference.

[0048] The polyisobutylene moiety in the dispersants of the present disclosure can also have a molecular weight distribution (MWD), also known as the polydispersity index, as determined by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). In some methods or embodiments, a suitable polyisobutylene moiety can have an Mw / Mn of less than about 3.0, or less than about 2.8, or less than about 2.5, and in other methods, a suitable polyisobutylene substituent has a polydispersity of about 1.5 to about 3.0, or about 2.0 to about 3.0.

[0049] The dicarboxylic acids or acid anhydrides suitable for forming the dispersant in the present invention may 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, mesaconic acid, ethyl maleic anhydride, dimethyl maleic anhydride, ethyl maleic acid, dimethyl maleic acid, hexyl maleic acid, etc., including the corresponding acid halides and C 1 -C 4 aliphatic esters. In some processes, the molar ratio of the dicarboxylic acid or acid anhydride to the hydrocarbyl moiety in the reaction mixture used to prepare the hydrocarbyl-dicarboxylic acid or acid anhydride can vary widely. Thus, the feed molar ratio can vary from 5:1 to 1:5, such as from 3:1 to 1:3. In some embodiments, particularly suitable molar ratios of the acid or acid anhydride to the hydrocarbyl moiety are from 1:1 to less than 1.6:1. In other embodiments, another useful feed molar ratio of the dicarboxylic acid or acid anhydride to the hydrocarbyl moiety 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.

[0050] Any of a number of polyalkylene polyamines can be used to prepare the dispersant additives of the present invention. Non-limiting exemplary polyamines can include aminoguanidine bicarbonate (AGBC), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), and heavy polyamines. Heavy polyamines can comprise a mixture of polyalkylene polyamines with a small amount of polyamine oligomers, such as TEPA and PEHA, but mainly oligomers having seven or more nitrogen atoms, two or more primary amines per molecule, and a more extensive branching than conventional polyamine mixtures. Generally, these heavy polyamines have an average of 6.5 nitrogen atoms per molecule. Other non-limiting polyamines useful for preparing hydrocarbyl-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 the hydrocarbyl-dicarboxylic acid or acid anhydride to the polyalkylene polyamine can be from about 1:1 to about 3.0:1. In one embodiment, the dispersant in the present disclosure described herein can be the reaction product of polyisobutenyl succinic anhydride (PIBSA) and a polyamine (e.g., heavy polyamine), wherein the feed molar ratio of the polyisobutenyl-substituted succinic anhydride to the polyamine is from about 1.7:1 to about 2.5:1.

[0051] As described above, the high molecular weight succinimide dispersants of the present invention can be post-treated with boron compounds. Suitable boron compounds for forming the dispersants of the present invention include any boron compound or mixture of boron compounds capable of introducing a boron-containing substance into an ashless dispersant. Any organic or inorganic boron compound capable of undergoing such a reaction can be used. Thus, boron oxide, boron oxide hydrate, boron trifluoride, boron tribromide, boron trichloride, HBF 4Boron acids such as boric acid (e.g., alkyl-B(OH) 2 or aryl-B(OH) 2 ), boric acid (i.e., H 3 BO 3 ), tetraboric acid (i.e., H 2 B 5 O 7 ), metaboric acid (i.e., HBO 2 ), ammonium salts of these boric acids, and esters of these boric acids. The use of complexes of boron trihalides with ethers, organic acids, inorganic acids, or hydrocarbons is a convenient method for introducing boron reactants into the reaction mixture. Such complexes are known, for example, boron trifluoride - diethyl ether, boron trifluoride - phenol, boron trifluoride - phosphoric acid, boron trichloride - chloroacetic acid, boron tribromide - dioxane, and boron trifluoride - methyl ethyl ether.

[0052] The high molecular weight succinimide dispersants of the present invention can also be post-treated with phosphorus compounds. Suitable phosphorus compounds for forming the dispersants of the present invention include phosphorus compounds or mixtures of phosphorus compounds capable of introducing phosphorus-containing substances into ashless dispersants. Thus, any organic or inorganic phosphorus compound capable of undergoing such a reaction can be used. Thus, these inorganic phosphorus compounds such as inorganic phosphoric acids and inorganic phosphorus oxides, including their hydrates, can be used. Typical organic phosphorus compounds include full esters and partial esters of phosphoric acid, such as phosphoric acid monoesters, phosphoric acid diesters, and phosphoric acid triesters, thiophosphoric acid, dithiophosphoric acid, trithiophosphoric acid, and tetrathiophosphoric acid; phosphorous acid monoesters, phosphorous acid diesters, and phosphorous acid triesters, thiophosphorous acid, dithiophosphorous acid, and trithiophosphorous acid; trihydrocarbylphosphine oxides; trihydrocarbylphosphine sulfides; monoalkylphosphonate and dialkylphosphonates (RPO(OR')(OR"), where R and R' are hydrocarbyl groups and R" is a hydrogen atom or a hydrocarbyl group), and their monothio, dithio, and trithio analogs; monoalkylphosphonite and dialkylphosphonites (RP(OR')(OR"), where R and R' are hydrocarbyl groups and R" is a hydrogen atom or a hydrocarbyl group) and their monothio and dithio analogs; and so on. Thus, compounds such as phosphorous acid (H 3 PO 3 , sometimes described as H 2 (HPO 3 ), sometimes called orthophosphorous acid or phosphonic acid), phosphoric acid (H 3 PO 4 , sometimes called orthophosphoric acid), hypophosphorous acid (H 4 P 2 O 6 ), metaphosphoric acid (HPO 3 ), pyrophosphoric acid (H 4 P 2 O 7 ), hypophosphinic acid (H 3PO 2 , sometimes referred to as hypophosphorous acid), pyrophosphorous acid (H 4 P 2 O 5 , sometimes referred to as pyrophosphoric acid), hypophosphorous acid (H 3 PO), tripolyphosphoric acid (H 5 P 3 O 10 ), tetrapolyphosphoric acid (H 5 P 4 O 13 ), trimetaphosphoric acid (H 3 P 3 O 9 ), phosphorus trioxide, phosphorus tetraoxide, phosphorus pentoxide, etc. Partial sulfur or all-sulfur analogues, such as thioacetic acid (H 3 PS 4 ), thiophosphoric acid (H 3 PO 3 S), dithiophosphoric acid (H 3 PO 2 S 2 ), trithiophosphoric acid (H 3 POS 3 ), sesquisulfide of phosphorus, diphosphorus heptasulfide and diphosphorus pentasulfide (P 2 S 5 , sometimes referred to as P 4 S 10 ), can also be used to form the dispersants of the present disclosure. Inorganic phosphorus halide compounds can also be used, such as PCl 3 , PBr 3 , POCl 3 , PSCl 3 , etc.

[0053] Similarly, organic phosphorus compounds can be used, such as mono-esters, di-esters and tri-esters of phosphoric acid (e.g., trialkyl phosphates, dialkyl monoacid phosphates, monoalkyl diacid phosphates and mixtures thereof), mono-esters, di-esters and tri-esters of phosphorous acid (e.g., trialkyl phosphites, dialkyl hydrogen phosphites, alkyl diacid phosphites and mixtures thereof), phosphonates (“primary” RP(O)(OR) 2 and “secondary” R 2 P(O)(OR)), phosphinites, phosphoryl halides (e.g., RP(O)Cl 2 and R 2 P(O)Cl), halogenated phosphites (e.g., (RO)PCl 2 and (RO) 2 PCl), halogenated phosphates (e.g., ROP(O)Cl 2 and (RO) 2P(O)Cl), tertiary pyrophosphates (e.g., (RO) 2 P(O)-O-P(O)(OR) 2 ), and fully sulfurized or partially sulfurized analogs of any of the foregoing organophosphorus compounds, etc., wherein each hydrocarbyl group contains up to 100 carbon atoms, preferably up to 50 carbon atoms, more preferably up to 24 carbon atoms, and most preferably up to 12 carbon atoms. Halophosphorus halides (e.g., hydrocarbyl tetraphosphorus halides, dihydrocarbyl triphosphorus halides, and trihydrocarbyl diphosphorus halides) and halophosphines (monohalophosphines and dihalophosphines) can also be used.

[0054] In one embodiment, the relatively high molecular weight succinimide dispersant of the fluids herein includes at least one polyisobutenyl moiety having a number average molecular weight of at least about 2000, and in other methods from about 2000 to about 3000, or in additional methods from about 2000 to about 2300, and having from about 0.5 wt% to about 1 wt% nitrogen, from about 0.05 wt% to about 0.25 wt% boron, and from about 0.20 wt% to about 0.45 wt% phosphorus, or in another embodiment, includes at least one polyisobutenyl moiety having a number average molecular weight of at least about 2000 to 2300, and having from about 0.60 wt% to about 0.90 wt% nitrogen, from about 0.10 wt% to about 0.20 wt% boron, and from about 0.25 wt% to about 0.40 wt% phosphorus.

[0055] In some embodiments, the relatively high molecular weight dispersants described herein can account for about 40 wt% to about 70 wt% of the additive concentrate. In some embodiments, the relatively high molecular weight succinimide dispersant described herein includes at least a polyisobutenyl moiety having a number average molecular weight of from about 2000 to about 2300, and having from about 0.6 wt% to about 0.9 wt% nitrogen, from about 0.10 wt% to about 0.20 wt% boron, and from about 0.25 wt% to about 0.40 wt% phosphorus, and can account for about 40 wt% to about 70 wt% of the additive concentrate. In some embodiments, the relatively high molecular weight succinimide dispersant described herein includes at least one polyisobutenyl moiety having a number average molecular weight of from about 2000 to about 2300, and delivers from about 3000 ppm to about 5400 ppm nitrogen, from about 600 ppm to about 1000 ppm boron, and from about 1400 ppm to about 2450 ppm phosphorus to the additive concentrate.

[0056] In some embodiments, the relatively high molecular weight dispersants described herein comprise from about 2.0% to about 4.0% of an electric motor lubricating fluid and deliver from about 150 ppm to about 300 ppm of nitrogen, from about 70 ppm to about 140 ppm of phosphorus, and from about 30 ppm to about 60 ppm of boron. As shown in the examples below, when such succinimide dispersants are mixed with other fluid components, particularly selected amounts of sulfur, boron, nitrogen, and / or phosphorus, the lubricant achieves passing wear performance, conductivity performance, and oxidation stability.

[0057] Amine salt of phosphate ester:

[0058] The electric motor lubricating fluid herein further comprises a first phosphorus-providing additive in an amount to provide from about 40 ppm to about 70 ppm of phosphorus to the fluid from the amine salt. In each method or embodiment, the first phosphorus-providing additive is in the form of an amine salt of a phosphate ester. In some methods, the amine salt of the phosphate ester can include one or more monoalkyl phosphates, dialkyl phosphates, and / or mixtures thereof, wherein the alkyl group thereof can be straight-chain, branched-chain, or cyclic. The fluid herein may also include other compounds that provide phosphorus, but in some embodiments, the amine salt of the phosphate ester herein provides from about 20 wt% to about 40 wt% of the total phosphorus in the electric motor lubricating fluid.

[0059] In each method or embodiment, an exemplary amine salt of a phosphate ester can be represented by Formula I

[0060]

[0061] wherein R of Formula I 3 and R 4 can independently be hydrogen or a straight-chain, branched-chain, or cyclic hydrocarbon group; m of Formula I is an integer from 0 to 1, p of Formula I is an integer from 1 to 2, and m + p equals 2; R of Formula I 5 、R 6 、R 7 and R 8 can independently be hydrogen or a hydrocarbon group, and at least one of R of Formula I 5 to R 8 is a hydrocarbon group. Examples of suitable alkyl or hydrocarbon groups for R of Formula I 3 and / or R 4 include straight-chain or branched-chain alkyl groups such as, but not limited to, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and / or decyl. In a further exemplary method, R of Formula I 3 and R 4It can be a cyclic hydrocarbon group and examples include cyclopentyl, cyclohexyl, cycloheptyl, methylcyclopentyl, dimethylcyclopentyl, methylcyclopentyl, dimethylcyclopentyl, methylethylcyclopentyl, diethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, methylethylcyclohexyl, diethylcyclohexyl, methylcycloheptyl, dimethylcycloheptyl, methylethylcycloheptyl, and / or diethylcycloheptyl. In some methods or embodiments, suitable amine salts of phosphate esters are mixtures of monoalkyl and dialkyl phosphates. As described above, the monoalkyl and dialkyl can be straight-chain, branched-chain, or cyclic.

[0062] The amine salts of phosphate esters can be derived from primary amines, secondary amines, or tertiary amines, or mixtures thereof. Exemplary amines suitable for the salts can be aliphatic, cyclic, aromatic, or non-aromatic, but are generally aliphatic amines. Examples of suitable primary amines include ethylamine, propylamine, butylamine, 2-ethylhexylamine, bis-(2-ethylhexyl)amine, octylamine, and dodecylamine, as well as fatty amines such as n-octylamine, n-decylamine, n-dodecylamine, n-tetradecylamine, n-hexadecylamine, n-octadecylamine, or oleylamine. Examples of suitable secondary amines include dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, methylethylamine, ethylbutylamine, N-methyl-1-amino-cyclohexane, and / or ethylpentylamine. Secondary amines can also be cyclic amines such as piperidine, piperazine, and morpholine. Examples of suitable tertiary amines can include tri-n-butylamine, tri-n-octylamine, tridecylamine, trilaurylamine, tricetylamine, and / or dimethyloleylamine.

[0063] In some methods, the amine of formula I above can be such that R 5 、R 6 、R 7 or R 8 at least one of the groups is a C 10 to C 20 alkyl group, and in other methods or embodiments, R 5 、R 6 、R 7 or R 8 groups of formula I are independently C 10 to C 20 alkyl groups. In some embodiments, at least two of the R 5 、R 6 、R 7 or R 8 groups of formula I are independently C 12 to C 14 alkyl groups.

[0064] The amine salts of phosphate esters can be prepared by reacting a suitable phosphorus compound with an amine to form the amine salt of the phosphate ester. In one embodiment, the amine salt of the phosphate ester can have formula I, where R 3 and R 4 can independently be C6 or hydrogen; m is an integer from 0 to 1, p is an integer from 1 to 2, and m + p equals 2; R 5 、R 6 、R 7 and R 8 may independently be hydrogen or a hydrocarbyl group of C 12 to C 14 and R 5 to R 8 at least one of which is a hydrocarbyl group of C 12 to C 14 .

[0065] In an embodiment, the amine salt of the phosphate ester may be present in the additive concentrate in an amount of 2 wt% to about 3 wt% or about 2.2 wt% to about 2.5 wt%. The amine salt of the phosphate ester may deliver about 1000 ppm to about 1500 ppm of phosphorus or about 1000 ppm to about 1250 ppm of phosphorus to the additive concentrate.

[0066] In each method, the amine salt of the phosphate ester may be present in the electric motor lubricating fluid herein in an amount of at least about 0.1 wt% to about 0.3 wt% or about 0.1 wt% to about 0.25 wt% of the lubricating composition. The amine salt of the phosphate ester may deliver about 50 ppm to about 150 ppm of phosphorus or about 50 ppm to about 125 ppm of phosphorus to the lubricating composition.

[0067] Ashless dialkyldithiophosphate :

[0068] In each method or embodiment, the electric motor lubricating fluid herein may further comprise a second phosphorus donating additive in the form of an acidic thiophosphate or thiophosphate. In one method or one embodiment, the second phosphorus donating additive may be an ashless, amine-free dialkyldithiophosphoric acid ester or a sulfur-containing phosphate ester.

[0069] The acidic thiophosphate, thiophosphate or sulfur-containing phosphate ester of the second phosphorus compound may have one or more sulfur-phosphorus bonds. In one embodiment, the sulfur-containing phosphate ester may be an acidic thiophosphate, thiophosphate, thiophosphoric acid or a salt thereof. The thiophosphate may be a dithiophosphate. In some more specific methods, the acidic thiophosphate or thiophosphate may have the structure of formula II or a salt thereof

[0070]

[0071] wherein R 4 and R 5 each independently is a straight-chain or branched-chain C 1 to C 10 hydrocarbyl group, and R 7 of formula II is C 1to C 10 a straight-chain or branched carboxyl group or C 1 to C 10 a straight-chain or branched alkyl ester group of an alkanoic acid. Preferably, R 4 and R 5 in formula II are each C 3 to C 8 a straight-chain or branched alkyl group and R 7 in formula II is derived from 2-methylpropanoic acid, such that the phosphorus product (or its salt) has the structure of formula II below:

[0072]

[0073] wherein R 4 and R 5 in the above formula II are independently C 3 to C 8 a straight-chain or branched alkyl group (preferably, a branched C 4 group), and R 6 in the above formula II is -H or -CH 3 . In some methods or embodiments, the second phosphorus product is preferably 3-[[bis(2-methylpropoxy)phosphinothioyl]thio]-2-methyl-propanoic acid.

[0074] In some methods, an oil-soluble phosphorus antiwear additive comprising a zinc-free dialkyl dithiophosphate is prepared by a method comprising the steps of: (a) reacting an organic hydroxy compound with phosphorus pentasulfide (in some forms, its monomer or dimer) to form a reaction product, and further reacting the reaction product with an unsaturated carboxylic acid to form an oil-soluble phosphorus antiwear additive comprising a zinc-free dialkyl dithiophosphate.

[0075] Suitable organic hydroxy compounds can include normal straight-chain alcohols, branched-chain alcohols, hydroxyaryl compounds (such as phenol and naphthol), substituted aryl hydroxy compounds (such as dipentylphenol), or any other hydroxy organic material in which the hydroxy group will react with phosphorus pentasulfide. In one method, the starting alcohol is a saturated alcohol or a substituted aryl hydroxy compound, such as an aryl hydroxy compound substituted with a saturated alkyl radical. In some methods, the organic hydroxy compound can be C 1 to C 10 (in other methods, C 1 to C 6)Straight-chain or branched-chain 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, dodecanol, octadecanol, 2-ethylhexanol, 4-methyl-2-pentanol, phenyl alcohol, butylphenyl alcohol, cyclohexanol, methylcyclopentanol, allyl alcohol, butenyl alcohol, or combinations thereof. Preferred organic hydroxy compounds herein include C 1 to C 4 alcohols, such as ethanol, propanol, or isopropanol, and most preferably, the organic hydroxy compound is isobutanol.

[0076] Suitable unsaturated carboxylic acids that form the oil-soluble phosphorus antiwear additives of the present disclosure may include a variety of unsaturated carboxylic acids or fatty acids. Preferred unsaturated carboxylic acids may include C 1 to C 20 unsaturated fatty acids, such as acrylic acid, methacrylic acid, 2-ethylacrylic acid, or combinations thereof, and most preferably methacrylic acid. (As used herein, (meth)acrylic acid refers to acrylic acid or methacrylic acid).

[0077] In some embodiments, the second phosphorus-providing additive is an acidic thiophosphate or thiophosphonate, which is present in the additive concentrate in an amount that provides 800 ppm to 1300 ppm of phosphorus and less than 2800 ppm of sulfur to the additive concentrate. In another embodiment, the second phosphorus-providing additive is an acidic thiophosphate or thiophosphonate, which is present in the additive concentrate in an amount that provides 900 ppm to 1200 ppm of phosphorus and less than 2500 ppm of sulfur to the additive concentrate. In one method, the additive concentrate contains from about 0.80 wt% to about 1.75 wt% of an ashless dialkyldithiophosphate compound, and in other methods, from about 0.9 wt% to about 1.40 wt%, from about 1.0 wt% to about 1.3 wt% of an ashless dialkyldithiophosphate compound.

[0078] In each method or embodiment, the electric motor lubricating fluid herein may further contain a second phosphorus-providing additive in the form of an ashless dialkyldithiophosphate compound in an amount that provides from about 40 ppm to about 70 ppm of phosphorus and less than 160 ppm of sulfur to the fluid. In some embodiments, the electric motor lubricating fluid herein may contain a second phosphorus-providing additive in the form of an ashless dialkyldithiophosphate compound in an amount that provides from about 50 ppm to about 65 ppm of total phosphorus and less than 140 ppm of sulfur. In one method or one embodiment, the electric motor lubricating fluid contains from about 0.03 wt% to about 0.1 wt% of an ashless dialkyldithiophosphate compound, and in other methods, from about 0.04 wt% to about 0.08 wt%.

[0079] Sulfur - donating additive :

[0080] The electric motor lubricating fluid contains a sulfur - donating additive. In the various methods or embodiments herein, the sulfur - donating additive can be one or more thiadiazole compounds or their hydrocarbyl - substituted derivatives in an amount that provides sulfur to the lubricating fluid herein but not more than about 950 ppm of sulfur. In other methods, the sulfur - donating compound can be a mixture of thiadiazole compounds or their hydrocarbyl - substituted derivatives. Examples of thiadiazole compounds that can be used include, but are not limited to, 2,5 - dimercapto - 1,3,4 - thiadiazole, 2 - mercapto - 5 - hydrocarbylthio - 1,3,4 - thiadiazole, 2 - mercapto - 5 - hydrocarbyldithio - 1,3,4 - thiadiazole, 2,5 - bis(hydrocarbylthio)-1,3,4 - thiadiazole, or 2,5 - bis(hydrocarbyldithio)-1,3,4 - thiadiazole. 1,3,4 - thiadiazole is generally synthesized from hydrazine and carbon disulfide by known methods. See, for example, US2,765,289; US2,749,311; US2,760,933; US 2,850,453; US2,910,439; US 3,663,561; US 3,862,798; and US 3,840,549.

[0081] In each method, the thiadiazole or its derivative includes one or more compounds having the structure of formula III:

[0082]

[0083] wherein each R in formula III 1 is independently hydrogen or sulfur, each R in formula III 2 is independently an alkyl group, n is an integer of 0 or 1, and if R 1 is hydrogen, the integer n for adjacent R 2 moieties is 0, and if R 1 is sulfur, the n for adjacent R 2 moieties is 1, and provided that at least one R 1 is sulfur. In other methods, the thiadiazole additive is a blend of compounds of formula IIIa and formula IIIb as shown below:

[0084]

[0085] wherein within formula IIIa, each integer n is 1, each R 1 is sulfur, and each R 2 is a C5 to C 15 alkyl group, preferably a C 8 to C 12 alkyl group; and

[0086]

[0087] Wherein in formula IIIb, an integer n is 1, and the associated R 2 group is C 5 to C 15 alkyl group (preferably C 8 to C 12 alkyl group), and another integer n is 0, and the two R 1 groups are sulfur. In some embodiments, the sulfur donor additive comprises a blend of formulas IIIa and IIIb, wherein formula Iva is the majority in the blend, and in other methods, the blend of IIIa and IIIb is about 75 wt% to about 90 wt% of IIIa and about 10 wt% to about 25 wt% of IIIb (or other ranges therein). In another method, the sulfur donor additive is 2,5-dimercapto-1,3,4-thiadiazole, which comprises a blend of 2,5-bis-(nonyl disulfide)-1,3,4-thiadiazole (such as about 75% to about 90%) and 2,5-mono-(nonyl disulfide)-1,3,4-thiadiazole (such as about 10% to about 25%).

[0088] The thiadiazole compound or its hydrocarbyl-substituted derivative is present in the electric motor lubricating fluid herein in an amount to deliver about no more than about 950 ppm of sulfur, no more than about 925 ppm of sulfur, or no more than about 900 ppm of sulfur and in other embodiments at least about 700 ppm of sulfur or at least about 800 ppm of sulfur (or other ranges therein). In one embodiment, the thiadiazole compound is 2,5-dimercapto-1,3,4-thiadiazole, and the thiadiazole compound or its hydrocarbyl-substituted derivative is present in the lubricating and cooling fluid in an amount to deliver about 700 ppm to about 950 ppm of sulfur, or about 750 ppm to about 900 ppm of sulfur (or other ranges therein).

[0089] Base oil :

[0090] The electric motor lubricating fluid herein comprises one or more base oils having lubricating viscosity. Base oils suitable for formulating the electric motor lubricating fluid for electric and / or hybrid electric motor vehicles according to the present disclosure or base oils having lubricating viscosity can be selected from any of suitable synthetic or natural oils or mixtures thereof having suitable lubricating viscosity. Natural oils can include animal and vegetable oils (such as castor oil, lard) and mineral oils, such as liquid petroleum and solvent-treated or acid-treated paraffinic, naphthenic or mixed paraffinic-naphthenic type mineral lubricating oils. Oils derived from coal or shale can also be suitable. In addition, oils derived from the gas-to-liquid process are also suitable. The base oil can have a kinematic viscosity of about 2 cSt to about 15 cSt at 100 °C as measured by ASTM D2270-10.

[0091] The base oil used in the present invention described herein can be a single base oil or can be a mixture of two or more base oils. One or more base oils can be selected from any of the Group III or Group IV base oils specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. These base oil groups are shown in Table 1 below:

[0092] Table 1

[0093]

[0094] In one variant, the base oil can be selected from Group III API base oils, or Group IV API base oils, or a mixture of these base oils. Alternatively, the base oil can be a mixture of two or more of Group III API base oils or two or more of Group IV API base oils.

[0095] Group III API base oils can include oils derived from Fischer-Tropsch synthesized hydrocarbons. The Fischer-Tropsch synthesized hydrocarbons are prepared from synthesis gas containing H 2 and CO using a Fischer-Tropsch catalyst. Such hydrocarbons generally require further processing to be used as base oils. These types of oils are commonly referred to as gas-to-liquid (GTL). For example, the hydrocarbons can be hydroisomerized using the methods disclosed in U.S. Patent Nos. 6,103,099 or 6,180,575; hydrocracked and hydroisomerized using the methods disclosed in U.S. Patent Nos. 4,943,672 or 6,096,940; dewaxed using the method disclosed in U.S. Patent No. 5,882,505; or hydroisomerized and dewaxed using the methods disclosed in U.S. Patent Nos. 6,013,171, 6,080,301, or 6,165,949.

[0096] Group IV API base oils, PAOs, are generally derived from monomers having 4 to 30, or 4 to 20, or 6 to 16 carbon atoms. Examples of PAOs that can be used in the present invention include those derived from octene, decene, mixtures thereof, etc. As measured by ASTM D2270-10, the PAO can have a kinematic viscosity at 100 °C of 2 to 15, or 3 to 12, or 4 to 8 cSt. Examples of PAOs include PAO having 4 cSt at 100 °C, PAO having 6 cSt at 100 °C, and mixtures thereof.

[0097] The base oil is combined with an additive composition as disclosed in the embodiments herein to provide a lubricating and cooling fluid for an electric motor system having an electric motor, gears, and clutches. Thus, based on the total weight of the lubricating and cooling fluid, the base oil can be present in the lubricating and cooling fluid in an amount greater than about 80% by weight. In some embodiments, based on the total weight of the lubricating and cooling fluid, the base oil can be present in the lubricating and cooling fluid in an amount greater than about 85% by weight.

[0098] Other additives

[0099] In addition to the components described above, the electric motor lubricating fluids described herein may also contain other additives for transmission fluid composition types. Such additives include, but are not limited to, antioxidants, viscosity modifiers, phosphorus-containing components, detergents, corrosion inhibitors, rust inhibitors, defoamers, demulsifiers, pour point depressants, seal swell agents, and additional dispersants, additional friction modifiers, and additional sulfur-containing components.

[0100] Antioxidants: In some embodiments, the electric motor lubricating fluid contains one or more antioxidants. Suitable antioxidants include phenolic antioxidants, aromatic amine antioxidants, sulfur-containing antioxidants, and organic phosphites, among others.

[0101] Examples of phenolic antioxidants include 2,6-di-tert-butylphenol, liquid mixtures of tert-butylphenols, 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-p-phenylenediamine, 4-isopropylaminodiphenylamine, phenyl-α-naphthylamine, phenyl-α-naphthylamine, and cycloalkylated diphenylamines. Examples include sterically hindered tert-butylated phenols, bisphenols, and cinnamic acid derivatives, and combinations thereof.

[0102] Aromatic amine antioxidants include, but are not limited to, diarylamines having the following formula:

[0103]

[0104] wherein R' and R” each independently represent a substituted or unsubstituted aryl group having 6 to 30 carbon atoms. Examples of substituents of the aryl group 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.

[0105] The aryl group is preferably a substituted or unsubstituted phenyl or naphthyl group, especially where one or two of these aryl groups are substituted by 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. Preferably one or two aryl groups are substituted, such as monoalkylated diphenylamine, dialkylated diphenylamine, or a mixture of monoalkylated diphenylamine and dialkylated diphenylamine.

[0106] Examples of diarylamines that can be used include, but are not limited to: diphenylamine; various alkylated diphenylamines, 3 - hydroxydiphenylamine, N - phenyl - 1,2 - phenylenediamine, N - phenyl - 1,4 - phenylenediamine, monobutyldiphenylamine, dibutyldiphenylamine, monooctyldiphenylamine, dioctyldiphenylamine, monononyldiphenylamine, dinonyldiphenylamine, monotetradecyldiphenylamine, ditetradecyldiphenylamine, phenyl - α - naphthylamine, monooctylphenyl - α - naphthylamine, phenyl - β - naphthylamine, monooctyldiphenylamine, dioctyldiphenylamine, p - oriented styryldiphenylamine, mixed butyloctyldiphenylamine, and mixed octylstyryldiphenylamine.

[0107] Sulfur - containing antioxidants include, but are not limited to, sulfurized olefins, which are 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.

[0108] α - olefins include, but are not limited to, any C 4 to C 25 α - olefins. The α - olefins can be isomerized before or during the sulfurization reaction. Structural and / or conformational isomers of α - olefins containing internal double bonds and / or branches can also be used. For example, isobutene is the branched - olefin counterpart of the α - olefin 1 - butene.

[0109] Sulfur sources that can be used for the sulfurization of olefins include: elemental sulfur, sulfur monochloride, sulfur dichloride, sodium sulfide, sodium polysulfide, and mixtures thereof, which are added together or at different stages of the sulfurization process.

[0110] 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, beef tallow, and combinations thereof.

[0111] The total amount of antioxidant in the lubricating and cooling fluids described herein can be present in an amount that delivers up to about 200 ppm of nitrogen or up to about 150 ppm of nitrogen or from about 100 ppm to about 150 ppm of nitrogen.

[0112] Friction Modifiers: In some embodiments, the electric motor lubricating fluid contains additional friction modifiers other than those included in the friction modifier systems described above. Suitable additional friction modifiers can include metal-containing and metal-free friction modifiers and can include, but are not limited to, imidazolines, amides, amines, succinimides, alkoxylated amines, alkoxylated ether amines, amine oxides, amidoamines, nitriles, betaines, quaternary amines, imines, amine salts, aminoguanidines, alkenolamides, phosphonates, metal-containing compounds, glycerol esters, sulfurized fatty compounds and olefins, sunflower oil, other naturally occurring vegetable or animal oils, dicarboxylic acid esters, esters or partial esters of polyols with one or more aliphatic or aromatic carboxylic acids, etc.

[0113] Suitable friction modifiers can contain a hydrocarbon group selected from linear, branched or aromatic hydrocarbon groups or mixtures thereof, and such hydrocarbon groups can be saturated or unsaturated. The hydrocarbon group can be composed of carbon and hydrogen or heteroatoms such as sulfur or oxygen. The hydrocarbon group can range from 12 to 25 carbon atoms. In some embodiments, the friction modifier can be a long-chain fatty acid ester. In another embodiment, the long-chain fatty acid ester can be a monoester or diester or (tri)glycerol ester. The friction modifier can be a long-chain fatty amide, long-chain fatty ester, long-chain fatty epoxide derivative or long-chain imidazoline.

[0114] Other suitable friction modifiers can include organic, ashless (metal-free), nitrogen-free organic friction modifiers. Such friction modifiers can include esters formed by reacting carboxylic acids and anhydrides with alkanols and generally contain a polar end group (e.g., carboxyl or hydroxyl) covalently bonded to a lipophilic hydrocarbon chain. Examples of organic ashless nitrogen-free friction modifiers are generally known as glycerol monooleate (GMO), which can contain monoester, diester and triester of oleic acid. Other suitable friction modifiers are described in U.S. Patent No. 6,723,685.

[0115] Amine-based friction modifiers can include amines or polyamines. Such compounds can have linear saturated or unsaturated hydrocarbon groups or mixtures thereof and can contain 12 to 25 carbon atoms. Other examples of suitable friction modifiers include alkoxylated amines and alkoxylated ether amines. Such compounds can have linear, saturated or unsaturated hydrocarbon groups, or mixtures thereof. They can contain from about 12 to about 25 carbon atoms. Examples include ethoxylated amines and ethoxylated ether amines.

[0116] Amines and amides can be used as such or in the form of an adduct or reaction product with a boron compound such as boron oxide, boron halide, borate monoalkyl ester, boric acid or boric acid monoalkyl ester, dialkyl ester or trialkyl ester. Other suitable friction modifiers are described in U.S. Patent No. 6,300,291.

[0117] If the additional friction modifier contains nitrogen, such additional friction modifier can be present in the lubricating and cooling fluid in any amount as long as the performance requirements are not impaired.

[0118] Detergents: The metal detergents that can be included in the electric motor lubricating fluids described herein typically include a polar head with a long hydrophobic tail, where the polar head contains a metal salt of an acidic organic compound. The salt can contain substantially stoichiometric amounts of metal, in which case they are typically described as normal or neutral salts and generally have a total base number or TBN (measured by ASTM D2896) of 0 to less than 150. By reacting an excess of a metal compound (such as an oxide or hydroxide) with an acidic gas (such as carbon dioxide), a large amount of metal base can be included. The resulting overbased detergent contains micelles of neutralized detergent around an inorganic metal base (such as hydrated carbonate) core. Such overbased detergents can have a TBN of 150 or higher, such as 150 to 450 or higher.

[0119] Detergents suitable for embodiments of the present invention include oil-soluble overbased, low-based, and neutral sulfonates, phenates, sulfurized phenates, and salicylates of metals, particularly alkali metals or alkaline earth metals (such as sodium, potassium, lithium, calcium, and magnesium). More than one metal can be present, such as calcium and magnesium. A mixture of calcium and / or magnesium with sodium can also be suitable. Suitable metal detergents can be overbased calcium or magnesium sulfonate with a TBN of 150 to 450 TBN, overbased calcium or magnesium phenate or sulfurized phenate with a TBN of 150 to 300 TBN, and overbased calcium or magnesium salicylate with a TBN of 130 to 350. Mixtures of these salts can also be used.

[0120] The metal-containing detergent can be present in the lubricating and cooling fluid in an amount sufficient to improve the rust prevention performance of the fluid. Based on the total weight of the lubricating and cooling fluid, the metal-containing detergent can be present in the fluid in an amount sufficient to provide up to 90 ppm of alkali metal and / or alkaline earth metal. In one example, the metal-containing detergent can be present in an amount sufficient to provide from about 20 ppm to about 50 ppm of alkali metal and / or alkaline earth metal. In another embodiment, the metal-containing detergent can be present in an amount sufficient to provide from about 30 ppm to about 40 ppm of alkali metal and / or alkaline earth metal.

[0121] In one method, a preferred detergent can be a neutral to low-alkali sulfonate and, in some methods, calcium sulfonate. Suitable detergents can be calcium sulfonates having a TBN of 50 or less, such as from about 25 to about 30, and providing no more than about 50 ppm calcium to the lubricant. In other methods, the detergent can provide from about 25 ppm to about 40 ppm calcium, from about 30 ppm to about 40 ppm calcium, or from about 30 ppm to about 38 ppm calcium to the finished electric motor lubricating fluid or composition. In terms of the additive concentrate, the detergent can provide more than about 950 ppm calcium to the additive concentrate, or from about 500 ppm to about 950 ppm calcium, from about 550 ppm to about 900 ppm calcium, from about 600 ppm to about 800 ppm calcium, or from about 600 ppm to about 700 ppm calcium to the additive concentrate.

[0122] Corrosion inhibitor: A rust inhibitor or corrosion inhibitor can also be included in the electric motor lubricating fluids described herein. Such materials include monocarboxylic acids and polycarboxylic acids. Examples of suitable monocarboxylic acids are caprylic acid, capric acid, and lauric acid. Suitable polycarboxylic acids include dimer acids and trimer acids, such as those produced from acids such as tall oil fatty acid, oleic acid, linoleic acid, or the like.

[0123] Another useful type of rust inhibitor can be alkenyl succinic acid and alkenyl succinic anhydride corrosion inhibitors, such as, for example, tetrapropenyl succinic acid, tetrapropenyl succinic anhydride, tetradecenyl succinic acid, tetradecenyl succinic anhydride, hexadecenyl succinic acid, hexadecenyl succinic anhydride, and the like. Also useful are half esters of alkenyl succinic acids having 8 to 24 carbon atoms in the alkenyl group with alcohols such as polyethylene glycol. Other suitable rust inhibitors or corrosion inhibitors include ether amines, acid phosphates, amines, polyethoxylated compounds such as ethoxylated amines, ethoxylated phenols, and ethoxylated alcohols, imidazolines, amino succinic acids, or their derivatives, and the like. Mixtures of such rust inhibitors or corrosion inhibitors can be used. When present in the lubricating compositions described herein, the total amount of corrosion inhibitor can range from up to 2.0 wt% or from 0.01 wt% to 1.0 wt% based on the total weight of the lubricating composition.

[0124] Viscosity modifier: The electric motor lubricating fluid can optionally contain one or more viscosity modifiers. Suitable viscosity modifiers can include polyolefins, olefin copolymers, ethylene / propylene copolymers, polyisobutene, hydrogenated styrene-isoprene polymers, styrene / maleate copolymers, hydrogenated styrene / butadiene copolymers, hydrogenated isoprene polymers, alpha-olefin maleic anhydride copolymers, polymethacrylates, polyacrylates, polyalkylstyrenes, hydrogenated alkenyl aryl conjugated diene copolymers, or mixtures thereof. Viscosity modifiers can include star polymers, and suitable examples are described in U.S. Publication No. 2012 / 0101017A1.

[0125] In addition to or in place of the viscosity modifier, the electric motor lubricating fluids described herein may optionally contain one or more dispersant viscosity modifiers. Suitable dispersant viscosity modifiers can include functionalized polyolefins, such as ethylene-propylene copolymers functionalized with the reaction product of an acylating agent (such as maleic anhydride) and an amine; polymethacrylates functionalized with an amine, or esterified maleic anhydride-styrene copolymers reacted with an amine.

[0126] Based on the total weight of the lubricating and cooling fluid, the total amount of the viscosity modifier and / or dispersant viscosity modifier (when present) can be up to about 1.0 wt%, or up to about 0.5 wt%, or up to about 0.3 wt%.

[0127] 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 the demulsifier in the lubricating and cooling fluid can be up to about 0.05 wt%, or up to about 0.02 wt%, or less than about 0.015 wt% based on the total weight of the lubricating and cooling fluid.

[0128] Antifoaming agents: Antifoaming agents for reducing or preventing the formation of stable foams include siloxanes, polyacrylates, or organic polymers. Foam inhibitors that can be used in the compositions of the present invention disclosed herein include copolymers of polysiloxane, ethyl acrylate, and 2-ethylhexyl acrylate, and optionally vinyl acetate. When present, the amount of the antifoaming agent in the lubricating and cooling fluid can be up to about 0.1 wt%, or up to about 0.05 wt%, or less than about 0.04 wt% based on the total weight of the lubricating and cooling fluid.

[0129] Pour point depressants: The electric motor lubricating fluid may optionally contain one or more pour point depressants. Suitable pour point depressants can include esters of maleic anhydride-styrene, polymethacrylates, polymethyl methacrylates, polyacrylates, or polyacrylamides, or mixtures thereof. Based on the total weight of the lubricant, the pour point depressant (when present) can be present in an amount of about 0.001 wt% to about 0.04 wt%.

[0130] Generally, the lubricating and cooling fluids described herein can include additive components within the ranges listed in Table 2.

[0131] Table 2

[0132]

[0133] The percentages of the above components represent the weight percentages of the components based on the total weight of the lubricating and cooling fluid containing the components. The 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 appropriate to use an additive concentrate (i.e., an additive plus a diluent, such as a hydrocarbon solvent) to blend all the components simultaneously. The use of an additive concentrate takes advantage of the compatibility provided by the combination of the ingredients when in the form of an additive concentrate. In addition, the use of the concentrate reduces the blending time and the likelihood of blending errors.

[0134] As described above, additive concentrates comprising relatively high - molecular - weight succinimide dispersants, amine salts of phosphoric esters, ash - less dialkyldithiophosphates, and thiadiazoles or their derivatives have a much higher viscosity than is typically used in vehicle lubricants having a kinematic viscosity at 100 °C (kV100 °C) of about 4.5 cSt or less, about 3.5 cSt or less, or about 3.0 cSt or less. In some methods, the additive concentrates of such components herein have a kV100 °C of about 15 cSt to about 80 cSt, but when used in the finished fluid having the elemental relationship, the electric - motor lubricating fluids herein still have a finished kV100 °C of about 4.5 cSt or less, about 3.5 cSt or less, or about 3.0 cSt or less, while having improved wear performance, conductivity, and oxidation stability. In some embodiments, the ratio of the kV100 °C of the additive concentrate to the kV100 °C of the finished fluid is about 5:1 to about 30:1. Any embodiment of the electric - motor lubricating fluids herein exhibits only a slight viscosity change after aging, such as a viscosity change of about 0.10 cSt or less (e.g., 0.01 cSt to 0.1 cSt, or 0.04 cSt to 0.08 cSt) for the fluid according to CEC L - 48 - A after aging at 170 °C to 180 °C for at least 192 hours. The electric - motor lubricating fluids herein also achieve a seizure load stage of at least 8 in the FZG A10 / 16.6R / 90 scuffing resistance test of CEC L - 84 - 02. Finally, the electric - motor lubricating fluids herein also have a conductivity of about 60 nS / M or less (e.g., about 20 nS / M to about 60 nS / M), as measured by a modified conductivity test according to ASTM D2624 - 15 using the electric - motor lubricating fluid and measured at 20 Hz and about 100 °C using a Fluconepsilon tester or equivalent. Surprisingly, such low - viscosity fluids with low conductivity and high oxidation stability can achieve the above - acceptable performance in the FZG A10 / 16.6R / 90 scuffing resistance test of CEC L - 84 - 02.

[0135] Examples

[0136] The present disclosure and many of its advantages can be better illustrated by the following examples. The following 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 devices described in these examples can be used. Unless otherwise specified or obvious from the context of the discussion in the following examples and throughout the present disclosure, all percentages, ratios, and parts mentioned in the present disclosure are by weight.

[0137] To demonstrate how a high molecular weight dispersant can be used in low viscosity fluids to achieve tested wear performance and conductivity, the systems herein compare fluids of nitrogen, boron, sulfur, and / or phosphorus having various elemental relationships to evaluate the wear performance, oxidation stability, and conductivity of fluids in extremely low viscosity fluids having a kV100°C of about 4.5 cSt or less, about 3.5 cSt or less, about 3.0 cSt or less, or about 2.9 cSt or less. The FZG scuff resistance, oxidation viscosity stability, and conductivity of the formulations are evaluated.

[0138] The FZG scuff resistance test is used to evaluate the scuff load capacity of a lubricant and is conducted according to the A10 / 16.6R / 90 test of CECL-84-02. The results are reported as the failure load stage, and better results are obtained for samples having a higher failure load stage.

[0139] Oxidation viscosity stability is used to evaluate the difference between the initial viscosity and the final viscosity of the fluid according to CEC L-48-A-00 after aging for 192 hours under operating conditions of 170°C to 180°C, where the fluid of this example is aged at 170°C. A lower value indicates improved performance. Thus, a fluid having high oxidation stability exhibits only small viscosity changes measured before and after aging.

[0140] It is beneficial for an electric motor fluid to exhibit low conductivity. The conductivity of the fluid is measured according to a modified version of ASTM D2624-15 (testing the lubricant instead of fuel at 1.5 V, 20 Hz, and 100°C using Flucon Epsilon+).

[0141] Both the inventive and comparative formulations tested in Table 3 below contain different amounts of sulfurized components, phosphorus additives, detergents, and dispersants, as shown in Table 3. Each fluid also contains the same antioxidant, antifoaming agent, and process oil. The antioxidant and antifoaming agent are added to each fluid at the same treatment rate. The inventive and comparative formulations are tested in the same base oil to obtain finished fluids having a kinematic viscosity at 100°C as shown in the table below. The inventive formulation contains additives similar to the comparative formulation but differently balances the delivery of sulfur, phosphorus, and dispersant to achieve surprisingly improved wear performance, oxidation stability, and lubricant conductivity. Details of these components are described below:

[0142] · Sulfur component (S - 1) : 2,5-dimercapto-1,3,4-thiadiazole and / or its derivatives containing approximately 35 wt% sulfur, which is a 75:25 to 85:15 mixture of 2,5-bis-(nonyl dithio)-1,3,4-thiadiazole and 2,5-mono-(nonyl dithio)-1,3,4-thiadiazole.

[0143] · Dispersant 1 (Disp - 1) : A phosphorylated and borated succinimide dispersant made from a mixture of 950Mn polyisobutene, maleic anhydride, polyalkylene polyamine with an average of 6.5 nitrogen atoms per molecule, phosphorous acid, and boric acid. The dispersant has approximately 0.76 wt% phosphorus, approximately 0.35 wt% boron, and approximately 1.75 wt% nitrogen.

[0144] · Dispersant 2 (Disp - 2) : A phosphorylated and borated succinimide dispersant obtained from 2100Mn polyisobutene, maleic anhydride, a mixture of polyalkylene polyamine with an average of 6.5 nitrogen atoms per molecule, phosphorous acid, and boric acid. The dispersant has approximately 0.77 wt% nitrogen, approximately 0.15 wt% boron, and approximately 0.35 wt% phosphorus.

[0145] · Phosphorus additive 1 (P - 1) : Amine salts of phosphate esters, including a mixture of dihexyl phosphate and monohexyl phosphate with di- and / or tri-alkylated amines having C 12 to C 14 alkyls. The phosphorus source includes approximately 2.5 wt% nitrogen and approximately 4.9 wt% phosphorus.

[0146] · Phosphorus additive 2 (P - 2) : Ashless dialkyldithiophosphate, including at least 3-[[bis(2-methylpropoxy)phosphinyl]sulfanyl]-2-methylpropanoic acid.

[0147] · Detergent additive 1 (Det - 1) : Neutral calcium sulfonate having a TBN of about 25 to about 30 and about 2.6 wt% calcium.

[0148] All fluids tested herein include the same blend of Group III and Group IV base oils. As shown in the table below, all examples of the present invention exhibit improved wear resistance, conductivity performance, and oxidation stability compared to comparative examples that deliver too little or too much phosphorus and include relatively low molecular weight dispersant additives. All fluids are considered low viscosity fluids having a kV100°C (ASTM D445) of about 4.5 cSt or less.

[0149] Table 3: Fluid composition

[0150]

[0151] Measured according to ASTM D445 - kV at 100 °C

[0152] Table 4: Elemental analysis of fluid (calculated)

[0153]

[0154]

[0155] Table 5: Fluid properties

[0156] Invention 1 Invention 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 FZG, Scuffing load stage** 8 9 5 7 5 6 8 Δ Viscosity, cSt*** 0.04 0.08 0.05 0.06 0.17 0.13 0.16 Conductivity, nS / m**** 22 58 71 13 36 38 37

[0157] **CEC L - 84 - 022(A10 / 16.6R / 90)

[0158] ***Difference between the initial and final viscosities after aging measured according to CEC L - 48 - A

[0159] ****ASTM D2624 - 15(20 Hz, 100 °C) performed on a Flucon epsilon or equivalent tester

[0160] It should be understood that although the lubricating compositions and compositions of the present disclosure have been described in connection with their detailed description and the summary herein, the foregoing description is intended to be illustrative and not limiting of the scope of the present disclosure, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are also within the scope of the claims. The present specification and examples are intended to be illustrative only, with the true scope of the present disclosure being indicated by the appended claims.

[0161] After considering this specification and the practice of the embodiments disclosed herein, other embodiments of the present disclosure will be apparent to those skilled in the art. As used throughout this specification and the claims, "a" or "an" may refer to one or more than one. Unless otherwise indicated, all numbers expressing quantities of ingredients, properties, such as molecular weight, percentage, ratio, reaction conditions, etc., used in this specification should be understood to be modified in all instances by the term "about", whether or not the term "about" is present. Thus, unless indicated to the contrary, the numerical parameters set forth in this specification are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Although the numerical ranges and parameters setting forth the broad scope of the present disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviations found in their corresponding test measurements.

[0162] It should be understood that each component, compound, substituent, or parameter disclosed herein should be construed as being disclosed for use individually or in combination with one or more of each of the other components, compounds, substituents, or parameters disclosed herein.

[0163] It should be further understood that each range disclosed herein should be construed as a disclosure of each specific value within the disclosed range having the same significant figure numerical value. Thus, the range of 1 - 4 will be construed as a disclosure of the values 1, 2, 3, and 4 and any range of those values, such as 1 - 4, 1 - 3, 1 - 2, 2 - 4, 2 - 3, and so on.

[0164] It should be further understood that each lower limit of each range disclosed herein should be construed as being 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 disclosed herein. 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.

[0165] In addition, a specific amount / value of a component, compound, substituent, or parameter disclosed in this specification or in the examples should be construed as a disclosure of a lower or upper limit of a range, and thus can be combined with any other lower or upper limit or specific amount / value of a range for the same component, compound, substituent, or parameter disclosed elsewhere in this disclosure to form a range of that component, compound, substituent, or parameter.

Claims

1. An electric motor lubricating fluid suitable for use in an electric or hybrid electric vehicle, the electric motor lubricating fluid comprising: One or more base oils of lubricating viscosity: a succinimide dispersant derived from polyisobutylene having a number average molecular weight of 2,000 or greater, wherein the succinimide dispersant has 0.5 wt % to 1 wt % nitrogen and is post-treated with a phosphorus-containing compound and a boron-containing compound, and wherein the succinimide dispersant delivers 70 ppm to 140 ppm phosphorus and 150 ppm to 300 ppm nitrogen to the electric motor lubricating fluid; an amine salt of a phosphate ester, the amine salt of the phosphate ester providing 40 ppm to 70 ppm of phosphorus to the electric motor lubricating fluid; an oil-soluble phosphorus antiwear additive comprising an ashless dialkyl dithiophosphate, the oil-soluble phosphorus antiwear additive providing 40 ppm to 70 ppm phosphorus to the electric motor lubricating fluid; a sulfur-donating additive comprising a thiadiazole or a derivative thereof, said sulfur-donating additive providing up to 950 ppm of sulfur to said electric motor lubricating fluid; and wherein the electric motor lubricating fluid has a kV100°C of 4.5 cSt or less and 150 ppm to 250 ppm total phosphorus.

2. The electric motor lubricating fluid of claim 1, wherein the amine salt of the phosphate ester has a structure of Formula I or a solvate or hydrate thereof: in R1 and R2 are independently hydrogen or a linear, branched or cyclic hydrocarbon group; m is an integer from 0 to 1, p is an integer from 1 to 2, and m+p is equal to 2; R3, R4, R5 and R6 are independently hydrogen or a hydrocarbon group, and at least one of R3 to R6 is a hydrocarbon group.

3. The electric motor lubricating fluid according to claim 2, wherein R1 and R2 are independently C3 to C 10 An alkyl group and wherein at least one of R3, R4, R5 and R6 is C 10 To C 20 Alkyl group.

4. The electric motor lubricating fluid of claim 1, wherein the number average molecular weight of the polyisobutylene is from 2,000 to 2,300. 5 . The electric motor lubricating fluid of claim 4 , wherein the electric motor lubricating fluid comprises 2 wt % to 4 wt % of the succinimide dispersant.

6. The electric motor lubricating fluid of claim 1 wherein the succinimide dispersant, the amine salt of the phosphate ester, the ashless dialkyl dithiophosphate, and the thiadiazole or derivative thereof are provided in an additive concentrate, and wherein the additive concentrate has a kV100°C of 15 cSt to 80 cSt.

7. The electric motor lubricating fluid of claim 6, wherein the ratio of the kV100°C of the additive concentrate to the kV100°C of the electric motor lubricating fluid is from 5:1 to 30:

1.

8. The electric motor lubricating fluid of claim 1, wherein the electric motor lubricating fluid has a viscosity change of less than 0.09 cSt after aging according to CEC L-48-A).

9. The electric motor lubricating fluid of claim 1, wherein the electric motor lubricating fluid achieves a failure load rating of at least 8 in the FZG A10 / 16.6R / 90 Scuff Resistance Test of CEC L-84-02.

10. The electric motor lubricating fluid of claim 1, wherein the electric motor lubricating fluid has an electrical conductivity of 60 nS / M or less, measured using a conductivity test of ASTM D2624-15 using the electric motor lubricating fluid using Flucon Epsilon+ at 1.5 V, 20 Hz, and 100°C.

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

12. The electric motor lubricating fluid of claim 1, wherein the ashless dialkyl dithiophosphate comprises a compound of formula II or a salt thereof: wherein R7 and R8 are independently C3 to C8 straight or branched chain alkyl groups, and R9 is -H or -CH3.

13. The electric motor lubricating fluid of claim 12, wherein the ashless dialkyl dithiophosphate is 3-[[bis(2-methylpropoxy)phosphinothioyl]thio]-2-methyl-propionic acid.

14. The electric motor lubricating fluid of claim 1, wherein the thiadiazole or derivative thereof comprises one or more compounds having a structure of Formula III: in Each R 10 independently hydrogen or sulfur; Each R 11 are independently alkyl groups; n is an integer of 0 or 1, and if R 10 is hydrogen, then the adjacent R 11 The integer n of the part is 0, and if R 10 is sulfur, then the adjacent R 11 Some of n is 1; and At least one of the R 10 For sulfur.

15. The electric motor lubricating fluid of claim 1 further comprising one or more metal-containing detergent additives providing no more than 50 ppm of calcium to the electric motor lubricating fluid.

16. An additive concentrate suitable for use in an electric motor lubricating fluid, the additive concentrate comprising: a succinimide dispersant derived from a high molecular weight polyisobutylene having a number average molecular weight of 2,000 or greater, wherein the succinimide dispersant has 0.5 wt % to 1 wt % nitrogen and is post-treated with a phosphorus-containing compound and a boron-containing compound, and wherein the succinimide dispersant is present in an amount to deliver 1400 ppm to 2450 ppm phosphorus and 3000 ppm to 5400 ppm nitrogen to the dispersant additive concentrate; an amine salt of a phosphate ester, the amine salt of the phosphate ester providing 1000 ppm to 1500 ppm of phosphorus to the additive concentrate; an oil-soluble phosphorus antiwear additive comprising an ashless dialkyl dithiophosphate, the oil-soluble phosphorus antiwear additive providing 800 ppm to 1300 ppm phosphorus to the additive concentrate; a sulfur-donating additive comprising a thiadiazole or a derivative thereof, said sulfur-donating additive providing sulfur to said additive concentrate, but not exceeding 18,000 ppm of sulfur; and The additive concentrate has a kV100°C of 15 cSt to 80 sCt.

17. The additive concentrate of claim 16, wherein the number average molecular weight of the high molecular weight polyisobutylene is from 2,000 to 2,300.

18. The additive concentrate of claim 16, wherein the succinimide dispersant comprises 40% to 70% by weight of the additive concentrate.

19. The additive concentrate of claim 16, further comprising one or more metal-containing detergent additives that provide no more than 950 ppm of calcium to the additive concentrate.

20. A method for lubricating a powertrain component including an electric motor, the method comprising: lubricating the powertrain component with an electric motor lubricating fluid, and wherein the electric motor lubricating fluid contacts a portion of the electric motor; The electric motor lubricating fluid comprises (i) one or more base oils of lubricating viscosity; (ii) a succinimide dispersant derived from a high molecular weight polyisobutylene having a number average molecular weight of 2,000 or greater, wherein the succinimide dispersant has 0.5 wt % to 1 wt % nitrogen and is post-treated with a phosphorus-containing compound and a boron-containing compound, and wherein the succinimide dispersant delivers 70 ppm to 140 ppm phosphorus and 150 ppm to 300 ppm nitrogen to the electric motor lubricating fluid; (iii) an amine salt of a phosphate ester, the amine salt of the phosphate ester providing 40 ppm to 70 ppm phosphorus to the electric motor lubricating fluid; (iv) an oil-soluble phosphorus antiwear additive comprising an ashless dialkyl dithiophosphate, the oil-soluble phosphorus antiwear additive providing 40 ppm to 70 ppm phosphorus to the electric motor lubricating fluid; and (v) a sulfur-donating additive comprising a thiadiazole or a derivative thereof, the sulfur-donating additive providing sulfur to the electric motor lubricating fluid, but not more than 950 ppm sulfur; and wherein the electric motor lubricating fluid has a kV100°C of 3.5 cSt or less, 150 ppm to 200 ppm total phosphorus, and a conductivity of 37 nS / M or less, as measured using the conductivity test of the electric motor lubricating fluid according to ASTM D2624-15 using Flucon Epsilon+ at 1.5 V, 20 Hz, and 100°C.

21. The method for lubricating a powertrain component including an electric motor according to claim 20, wherein the number average molecular weight of the high molecular weight polyisobutylene is from 2,000 to 2,300.

22. The method for lubricating a powertrain component including an electric motor according to claim 20, wherein the electric motor lubrication fluid comprises 2 wt% to 4 wt% of the succinimide dispersant.

23. The method for lubricating a powertrain component including an electric motor according to claim 20, wherein the succinimide dispersant, the amine salt of the phosphate ester, the oil-soluble phosphorus antiwear additive including an ashless dialkyl dithiophosphate, and the sulfur supplying additive including a thiadiazole or a derivative thereof are provided in an additive concentrate having a kV100°C of 15 cSt to 80 cSt.

24. The method for lubricating a powertrain component including an electric motor according to claim 23, wherein the ratio of the kV100°C of the additive concentrate to the kV100°C of the electric motor lubricating fluid is from 5:1 to 30:

1.

25. The method for lubricating a powertrain component including an electric motor according to claim 20, wherein the electric motor lubricating fluid has a viscosity change of less than 0.09 cSt per CEC L-48-A after aging.

26. The method for lubricating a powertrain component including an electric motor according to claim 20, wherein the electric motor lubricating fluid achieves a failure load rating of at least 8 in the FZG A10 / 16.6R / 90 Scuff Resistance Test of CEC L-84-02.

27. The method for lubricating a powertrain component including an electric motor according to claim 20, wherein the electric motor lubricating fluid further comprises one or more metal-containing detergent additives that provide no more than 50 ppm of calcium to the electric motor lubricating fluid.

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