ALCOXYLATED ALCOHOLS FOR INCREASING THE BREAKING STRENGTH OF A LUBRICANT

Description

[0001] The present invention relates a lubricant comprising a base stock selected from hydrocarbons, 50 to 1000 ppm water, and an alkoxylated alcohol, where the alcohol is alkoxylated with a hydrophobic epoxide selected from C 4 -C 20 epoxides. The invention also relates to a method for lubricating a mechanical device in an electric vehicle comprising the step of contacting the lubricant with the mechanical device; to a use of the alkoxylated alcohol for increasing the breakdown voltage of a lubricant comprising the basestock selected from the hydrocarbons; and to a use of the alkoxylated alcohol in a lubricant comprising the base stock selected from the hydrocarbons for reducing the electric discharge machining; and to a lubricant comprising a base stock selected from hydrocarbons which are selected from API Groups I, II, or III base stocks, 50 to 1000 ppm water, and an alkoxylated alcohol, where the alcohol is alkoxylated with a hydrophobic epoxide selected from C 4 -C 20 epoxides, and where the alcohol is a diol selected from C 2 -C 12 diol, polyethylene glycol, polypropylene glycol and polytetrahydrofurane..

[0002] The unintended flow of electric current (sometimes also called parasitic currents) in rolling bearings can damage the mechanical components and the lubricant. Typically bearing current events are in the form of arcing discharge current pulses which occur due to capacitive discharge breakdown of the lubricant. Such events are also known as electric discharge machining (EDM). As a result the lubricants get burned or the bearings are worn off.

[0003] In automotive industry frequency inverters are used to control variable speed inverter-fed electric motors and generators, and they may cause damage to the rolling bearings as a result of bearing currents. Typical observations include current-related damages, crater formation in the bearing raceway, the fluting across the raceway, and the oxidation of the lubricant in the contact zone between the rolling element and raceway

[0004] To avoid these problems the construction of bearings or rotating shafts was optimized: WO 2022 / 005935 suggested a grounding brush assembly to mitigate electric current in a rotating shaft in the presence of a viscous medium.

[0005] WO 2013 / 090997 suggested an earth assembly for an electric motor.

[0006] US2004 / 0056543 suggested an electromechanical device where a voltage reducing member is secured to a rotatable member.

[0007] US 2022 / 0064563 A1 describes a gear oil composition having a kinematic viscosity at 40°C in the range of ≥ 135 to ≤ 750 cSt when measured in accordance with ASTM D445, the gear oil composition comprising (a) ≥ 20.0 wt% to ≤ 94.0 wt% of at least one alkoxylated polytetrahydrofuran having a kinematic viscosity at 40°C in the range of ≥ 700 to ≤ 1300 cSt; and (b) ≥ 6.0 wt% to ≤ 76.0 wt% of at least one polyalphaolefin having a kinematic viscosity at 40°C in the range of ≥ 16 to 60 cSt; wherein the wt% are based on the total weight of the gear oil composition.

[0008] US 2017 / 0349850 A1 discloses a monophasic lubricating composition including a base oil, and oil chosen from alkylene glycol is (PAG) and a phase change material, in particular water. The monophasic lubricating composition can be used, in particular, for lubricating a vehicle engine. The publication indicates improved thermal performance relative to prior art lubricant compositions and also claims to help reduce fouling of the engine parts.

[0009] CN 114317078 A reveals a multifunctional oil-based fluid for electric vehicles, comprising base oil and selected additives. The fluid provides both dielectric cooling and lubrication for battery, motor, and transmission systems, enabling integrated single fluid operation with improved safety, thermal management, and wear protection.

[0010] The influence of lubricants on parasitic currents was also investigated: Bechev et al. "Characterization of electrical lubricant properties for modelling of electrical drive systems with rolling bearings" Bearing World Journal, 2018 (3), 93-106 investigated electrical lubricant properties relevant for parasitic bearing currents.

[0011] Gonda et al. "The Influence of Lubricant Conductivity on Bearing Currents in the Case of Rolling Bearing Greases" Lubricants, 2019 (7), 108-121, investigated the harmful currents in rolling bearings.

[0012] Object of the present invention was to provide a lubricant to overcome the above problems.

[0013] The object was solved by a method for lubricating a mechanical device in an electric vehicle comprising the step of contacting the lubricant with the mechanical device, where the lubricant comprises a base stock selected from hydrocarbons, 50 to 600 ppm water, and an alkoxylated alcohol, where the alcohol is a polytetrahydrofuran with 5 to 20 repeating units, and where the alcohol is alkoxylated with a hydrophobic epoxide which is dodecyl oxide, and where the lubricant comprises 5 to 30 wt% of the alkoxylated alcohol.

[0014] The object was solved by a lubricant comprising base stock selected from hydrocarbons which are selected from API Groups I, II, or III base stocks, 100 to 600 ppm water, and an alkoxylated alcohol, where the alcohol is a polytetrahydrofuran with 5 to 20 repeating units, and where the alcohol is alkoxylated with a hydrophobic epoxide which is dodecyl oxide, and where the lubricant comprises 5 to 30 wt% of the alkoxylated alcohol.

[0015] The lubricant is usually a substance capable of reducing friction between surfaces (preferably metal surfaces), such as surfaces of mechanical devices. A mechanical device may be a mechanism consisting of a device that works on mechanical principles. The lubricant is usually a lubricating liquid, lubricating oil or lubricating grease.

[0016] The lubricant can be used for various applications such as light, medium and heavy duty engine oils, industrial engine oils, marine engine oils, automotive engine oils, crankshaft oils, compressor oils, refrigerator oils, hydrocarbon compressor oils, very low-temperature lubricating oils and fats, high temperature lubricating oils and fats, wire rope lubricants, textile machine oils, refrigerator oils, aviation and aerospace lubricants, aviation turbine oils, transmission oils, gas turbine oils, spindle oils, spin oils, traction fluids, transmission oils, plastic transmission oils, passenger car transmission oils, truck transmission oils, industrial transmission oils, industrial gear oils, insulating oils, instrument oils, brake fluids, transmission liquids, shock absorber oils, heat distribution medium oils, transformer oils, fats, chain oils, minimum quantity lubricants for metalworking operations, oil to the warm and cold working, oil for water-based metalworking liquids, oil for neat oil metalworking fluids, oil for semi-synthetic metalworking fluids, oil for synthetic metalworking fluids, drilling detergents for the soil exploration, hydraulic oils, in biodegradable lubricants or lubricating greases or waxes, chain saw oils, release agents, molding fluids, gun, pistol and rifle lubricants or watch lubricants and food grade approved lubricants.

[0017] The lubricant comprises usually at least 50, 60, 70, 80 or 90 wt% of the base stock. The lubricant comprises usually up to 80, 90, 95, or 99 wt% of the base stock. The lubricant comprises usually 50-99, 50-95, 60-90 or 70-80 wt% of the base stock.

[0018] The base stock is selected from hydrocarbons. Suitable hydrocarbons are usually mixtures of higher alkanes from a mineral source (e.g. mineral oils), particularly a distillate of petroleum, or from synthetic sources (e.g. polyalphaolefins or GTL oils). Hydrocarbons can be naphthenic, paraffinic or aromatic in chemical structure. In industrial use a base stock normally contains a chemical composition which contains some proportion of all three oils (paraffinic, naphthenic and aromatic).

[0019] Naphthenic hydrocarbons are made up of methylene groups arranged in ring formation with paraffinic side chains attached to the rings. The pour point is generally lower than the pour point for paraffinic oils.

[0020] Paraffinic hydrocarbons comprise saturated, straight chain or branched hydrocarbons. The straight chain paraffins of high molecular weight raise the pour point of oils and are often removed by dewaxing.

[0021] Aromatic hydrocarbons are hydrocarbons of closed carbon rings of a semi-unsaturated character and may have attached side chains. This oil is more easily degraded than paraffinic and naphthalenic oils leading to corrosive by-products

[0022] In another form the hydrocarbons are GTL (gas-to-liquid) oils, which may be synthesized using the Fischer-Tropsch method of converting natural gas to liquid fuel. The GTL oils may be produced as follows: In the first stage a synthesis gas (a mixture of hydrogen and carbon monoxide) is manufactured from natural gas by partial oxidation. In the second stage the synthesis gas is converted into liquid hydrocarbons using a catalyst.The final stage is cracking and isomerisation, which "tailors" the molecule chains into products with desired properties. These GTL oils correspond to API Group 3 base oils, and Shell XHVI is an example of a commercial product.

[0023] Preferably, the hydrocarbon is selected from API Groups I, II, III or IV base stocks, or mixtures thereof. In particular, the hydrocarbon is selected from API Groups I, II, or III base stocks, or mixtures thereof. In another particular form, the hydrocarbon is selected from API Group III base stocks.

[0024] The definitions for the base stocks can be found in the American Petroleum Institute (API) publication "Engine Oil Licensing and Certification System", Industry Services Department, Fourteenth Edition, December 1996, Addendum 1, December 1998. Said publication categorizes base oils as follows: a) Group I base oils contain less than 90 percent saturates (ASTM D 2007) and / or greater than 0.03 percent sulfur (ASTM D 2622) and have a viscosity index (ASTM D 2270) greater than or equal to 80 and less than 120. b) Group II base oils contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulfur and have a viscosity index greater than or equal to 80 and less than 120. c) Group III base oils contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulfur and have a viscosity index greater than or equal to 120. d) Group IV base oils contain polyalphaolefins. Polyalphaolefins (PAO) include known PAO materials which typically comprise relatively low molecular weight hydrogenated polymers or oligomers of alphaolefins which include but are not limited to C2 to about C32 alphaolefins with the C8 to about C16 alphaolefins, such as 1-octene, 1-decene, 1-dodecene and the like being preferred. The preferred polyalphaolefins are poly-1-octene, poly-1-decene, and poly-1-dodecene. e) Group V base oils contain any base oils not described by Groups I to IV. Examples of Group V base oils include alkyl naphthalenes, alkylene oxide polymers, silicone oils, and phosphate esters.

[0025] The lubricant is usually free of a API Group V base stock. In another form the lubricant is comprises up to 20, 10, 5, or 1 wt% of an API Group V base stock.

[0026] In another form the lubricant is usually free of a API Group IV and V base stocks. In another form the lubricant is comprises up to 20, 10, 5, or 1 wt% of an API Group IV and V base stocks.

[0027] The base stock has usually a breakdown voltage of up to 1000, 500, 250, 150 or 100 Volt. The base stock has usually a breakdown voltage of at least 1, 3, 5, 10, or 20 Volt. The base stock has usually a breakdown voltage in the range of 1-1000 Volt, or 5-500 Volt, or 10-150 Volt. The breakdown voltage of the base stock is usually determined at a water concentration of below 5 ppm, in particular at 0 ppm.

[0028] The breakdown voltage of the base stock may be determined prior its use in the lubricant according to DIN EN 60156 ("Insulating liquids - Determination of the breakdown voltage at power frequency - Test method").

[0029] The lubricant comprises 50 to 600 ppm, or 100 to 600 ppm, or 150 to 600 ppm, or 200 to 600 ppm water.

[0030] The water content can be determined by the Karl Fischer method (DIN 51777 / 1 / ASTM D 1744). The water content may be determined at 20 °C.

[0031] The water is usually present in dissolved form in the lubricant.

[0032] The water in the lubricant may results from water traces in the base stock, in the lubricant additives or in the alkoxylated alcohol, or from the humidity in the air.

[0033] The water content in the lubricant can be adjusted for example by the use of desiccant breathers, which can be to attach to equipment (e.g. oil reservoir, oil drum). When the humid air gets through the breathers, the moisture in the air is then absorbed by a hygroscopic agent (e.g. a bed of silica gel). The water content in the lubricant may be adjusted by applying a vacuum to the lubricant, or by exluding air or water prior or during mixing of the components of the lubricant.

[0034] The lubricant comprises an alkoxylated alcohol, where the alcohol is alkoxylated with a hydrophobic epoxide which is dodecyl oxide.

[0035] The alcohol

[0036] is polytetrahydrofuran, which may have 6 to 16 repeating units.

[0037] The hydrophobic epoxide is dodecyl oxide.

[0038] The alcohol is alkoxylated with the hydrophobic epoxide which is dodecyloxide, and optionally in addition with propylene oxide.

[0039] In another preferred form the alcohol is alkoxylated with the hydrophobic epoxide which is dodecyloxide, and in addition with propylene oxide.

[0040] In another preferred form the alcohol is alkoxylated with the hydrophobic epoxide selected from dodecyl oxide, and in addition with propylene oxide.

[0041] The propylene oxide may be present up to 90, 80, 70, 65, 60, or 55 wt% based on the total amount of hydrophobic epoxide and propylene oxide. The propylene oxide may be present up to 85, 75, 70, or 65 mol% based on the total amount of hydrophobic epoxide and propylene oxide.S

[0042] Preferably, the alcohol is alkoxylated with the hydrophobic epoxide which is dodecyloxide, and optionally in addition with propylene oxide, where the propylene oxide may be present up to 90, 80, 70, 65, 60, or 55 wt% based on the total amount of hydrophobic epoxide and propylene oxide.

[0043] In another preferred form the alcohol is alkoxylated with the hydrophobic epoxide which is dodecyloxide, and optionally in addition with propylene oxide, where the propylene oxide may be present up to 85, 75, 70, or 65 mol% based on the total amount of hydrophobic epoxide and propylene oxide.

[0044] In another preferred form the alcohol is alkoxylated with the hydrophobic epoxide which is dodecyloxide, and in addition with propylene oxide, where the propylene oxide is present up to 90, 80, 70, 65, 60, or 55 wt% based on the total amount of hydrophobic epoxide and propylene oxide.

[0045] In another preferred form the alcohol is alkoxylated with the hydrophobic epoxide which is dodecyloxide, and in addition with propylene oxide, where the propylene oxide is present up to 85, 75, 70, or 65 mol% based on the total amount of hydrophobic epoxide and propylene oxide.

[0046] In another preferred form the alcohol is alkoxylated with the hydrophobic epoxide selected from dodecyl oxide, and in addition with propylene oxide, where the propylene oxide is present up to 85, 75, 70, or 65 mol% based on the total amount of hydrophobic epoxide and propylene oxide. In another preferred form the alcohol is alkoxylated with the hydrophobic epoxide selected from dodecyl oxide, and in addition with propylene oxide, where the propylene oxide is present up to 85, 75, 70, or 65 mol% based on the total amount of hydrophobic epoxide and propylene oxide.

[0047] The alkoxylated alcohol is an alkoxylated polytetrahydrofuran.

[0048] In a preferred form the alkoxylated alcohol is an alkoxylated polytetrahydrofuran of general formula (I) wherein mis an integer in the range of ≥ 1 to ≤ 30, m'is an integer in the range of ≥ 1 to ≤ 30, (m+m')is an integer in the range of ≥ 2 to ≤ 60, nis an integer in the range of ≥ 0 to ≤ 45, n'is an integer in the range of ≥ 0 to ≤ 45, (n+n')is an integer in the range of ≥ 0 to ≤ 80, pis an integer in the range of ≥ 0 to ≤ 25, p'is an integer in the range of ≥ 0 to ≤ 25, (p+p')is an integer in the range of ≥ 0 to ≤ 30, kis an integer in the range of ≥ 5 to ≤ 20, R 1< denotes an unsubstituted, linear or branched, alkyl radical having 10 carbon atoms, R 2< denotes -CH 2 -CH 3 , and R 3< identical or different, denotesa hydrogen atom or -CH 3 ,

[0049] whereby the concatenations denoted by k are distributed to form a block polymeric structure and the concatenations denoted by p, p', n, n', m and m' are distributed to form a block polymeric structure or a random polymeric structure.

[0050] Preferably the alkoxylated polytetrahydrofurane has a kinematic viscosity in the range of ≥ 200 mm 2< / s to ≤ 700 mm 2< / s, more preferably in the range of ≥ 250 mm 2< / s to ≤ 650 mm 2< / s, at 40 °C, determined according to ASTM D 445.

[0051] Preferably the alkoxylated polytetrahydrofurane has a kinematic viscosity in the range of ≥ 25 mm 2< / s to ≤ 90 mm 2< / s, more preferably in the range of ≥ 30 mm 2< / s to ≤ 80 mm 2< / s, at 100 °C, determined according to ASTM D 445.

[0052] Preferably the alkoxylated polytetrahydrofurane has a pour point in the range of ≥ - 60 °C to ≤ 20 °C, more preferably in the range of ≥ - 50 °C to ≤ 15 °C, determined according to DIN ISO 3016.

[0053] Preferably the alkoxylated polytetrahydrofurane has a weight average molecular weight Mw in the range of 500 to 20000 g / mol, more preferably in the range of 2000 to 10000 g / mol, most preferably in the range of 2000 to 7000 g / mol, even more preferably in the range of 4000 to 7000 g / mol determined, determined according to DIN 55672-1.

[0054] Preferably the alkoxylated polytetrahydrofurane has a polydispersity in the range of 1,05 to 1,60, more preferably in the range of 1,05 to 1,50, most preferably in the range of 1,05 to 1,45, determined according to DIN 55672-1.

[0055] k is an integer in the range of ≥ 5 to ≤ 20, even more preferably in the range of ≥ 6 to ≤ 16.

[0056] Preferably m is an integer in the range of ≥ 1 to ≤ 25 and m' is an integer in the range of ≥ 1 to ≤ 25, more preferably m is an integer in the range of ≥ 1 to ≤ 20 and m' is an integer in the range of ≥ 1 to ≤ 20.

[0057] Preferably (m+m') is an integer in the range of ≥ 3 to ≤ 65, more preferably (m+m') is an integer in the range of ≥ 3 to ≤ 50, even more preferably (m+m') is an integer in the range of ≥ 3 to ≤ 40.

[0058] Preferably the ratio of (m+m') to k is in the range of 0.3:1 to 6:1, more preferably in the range of 0.3:1 to 5:1, most preferably in the range of 0.3:1 to 4:1, even more preferably in the range of 0.3:1 to 3:1.

[0059] Preferably n is an integer in the range of ≥ 6 to ≤ 40 and n' is an integer in the range of ≥ 6 to ≤ 40, more preferably n is an integer in the range of ≥ 8 to ≤ 35 and p' is an integer in the range of ≥ 8 to ≤ 35.

[0060] Preferably (n+n') is an integer in the range of ≥ 10 to ≤ 80, more preferably (n+n') is an integer in the range of ≥ 15 to ≤ 70.

[0061] Preferably p is an integer in the range of ≥ 5 to ≤ 25 and p' is an integer in the range of ≥ 5 to ≤ 25, more preferably p is an integer in the range of ≥ 5 to ≤ 15 and p' is an integer in the range of ≥ 5 to ≤ 15.

[0062] Preferably (p+p') is an integer in the range of ≥ 10 to ≤ 30, more preferably (p+p') is an integer in the range of ≥ 15 to ≤ 30.

[0063] R 1< denotes an unsubstituted, linear alkyl radical having 10 carbon atoms.

[0064] In case the alkoxylated polytetrahydrofuran comprises units, wherein R 2< denotes -CH 2 -CH 3 , the ratio of (n+n') to k is in the range of 1.5:1 to 10:1, more preferably in the range of 1.5:1 to 6:1, most preferably in the range of 2:1 to 5:1.

[0065] In case the alkoxylated polytetrahydrofuran comprises units, wherein R 3< denotes -CH 3 , the ratio of (p+p') to k is in the range of 1.2:1 to 10:1, more preferably in the range of 1.2:1 to 6:1.

[0066] In another preferred form the alkoxylated alcohol is an alkoxylated polytetrahydrofuran of general formula (I) wherein mis an integer in the range of ≥ 1 to ≤ 25, m'is an integer in the range of ≥ 1 to ≤ 25, (m+m')is an integer in the range of ≥ 3 to ≤ 40, nis an integer in the range of ≥ 6 to ≤ 40, n'is an integer in the range of ≥ 6 to ≤ 40, (n+n')is an integer in the range of ≥ 12 to ≤ 70, pis an integer in the range of ≥ 0 to ≤ 25, p'is an integer in the range of ≥ 0 to ≤ 25, (p+p')is an integer in the range of ≥ 0 to ≤ 30, kis an integer in the range of ≥ 5 to ≤ 20, R 1< denotes an unsubstituted, linear alkyl radical having 10 carbon atoms, R 2< denotes -CH 2 -CH 3 , and R 3< denotes -CH 3 , whereby the concatenations denoted by k are distributed to form a block polymeric structure and the concatenations denoted by p, p', n, n', m and m' are distributed to form a block polymeric structure or a random polymeric structure, and

[0067] wherein the ratio of (m+m') to k is in the range of 0.3:1 to 4:1 and the ratio of (n+n') to k is in the range of 1.5:1 to 5:1.

[0068] In another preferred form the alkoxylated alcohol is an alkoxylated polytetrahydrofuran of general formula (I) wherein mis an integer in the range of ≥ 1 to ≤ 25, m'is an integer in the range of ≥ 1 to ≤ 25, (m+m')is an integer in the range of ≥ 3 to ≤ 50, nis an integer in the range of ≥ 0 to ≤ 45, n'is an integer in the range of ≥ 0 to ≤ 45, (n+n')is an integer in the range of ≥ 0 to ≤ 80, pis an integer in the range of ≥ 5 to ≤ 20, p'is an integer in the range of ≥ 5 to ≤ 20, (p+p')is an integer in the range of ≥ 10 to ≤ 30, kis an integer in the range of ≥ 5 to ≤ 20, R 1< denotes an unsubstituted, linear alkyl radical having 10carbon atoms, R 2< denotes -CH 2 -CH 3 , and R 3< denotes -CH 3 ,

[0069] whereby the concatenations denoted by k are distributed to form a block polymeric structure and the concatenations denoted by p, p', n, n', m and m' are distributed to form a block polymeric structure or a random polymeric structure, wherein the ratio of (m+m') to k is in the range of 0.3:1 to 4:1 and the ratio of (p+p') to k is in the range of 1.5:1 to 5:1.

[0070] The alkoxylated polytetrahydrofurans are usually obtainable by reacting at least one polytetrahydrofuran block polymer with dodecyl oxide and optionally at least one epoxide selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide in the presence of at least one catalyst. In case at least one epoxide selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide is used, the dodecyl oxide and the at least one epoxide selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide can either be added as a mixture of epoxides to obtain a random copolymer or in portions, whereby each portion contains a different epoxide, to obtain a block copolymer.

[0071] The alkoxylated alcohol is usually oil soluble, which can mean that, when mixed with the hydrocarbons in a weight ratio of 10:90, 50:50 and 90:10, the alkoxylated alcohols do not show phase separation after standing for 24 hours at room temperature for at least two weight rations out of the three weight ratios 10:90, 50:50 and 90:10.

[0072] The lubricant comprises 5 to 30 wtof the alkoxylated alcohol. In another form the lubricant comprises 5 to 20 wt% of the alkoxylated alcohol.

[0073] The lubricant is usually free of ionic liquids. Ionic liquids are usually salts having a melting point of less than 100°C at 1 bar. Ionic liquids can be liquid under normal conditions (1 bar, at room temperature). Ionic liquids may comprise at least one organic compound as cation, such as quaternary ammonium cations, e.g. pyridinium cations, pyridazinium cations, pyrimidinium cations, pyrazinium cations, imidazolium cations, pyrazolium cations, pyrazolinium cations, imidazolinium cations, thiazolium cations, triazolium cations, pyrrolidinium cations and imidazolidinium cations.

[0074] The lubricant may have a kinematic viscosity of 1 to 100 mm 2< / s at 100 °C, as may be determined according to ASTM D445.

[0075] The lubricant may further comprise in addition to the base stock selected from the hydrocarbons, the water and the alkoxylated alcohol a lubricant additive. Suitable lubricant additives may be selected from viscosity index improvers, polymeric thickeners, corrosion inhibitors, detergents, dispersants, anti-foam agents, dyes, wear protection additives, extreme pressure additives (EP additives), anti-wear additives (AW additives), friction modifiers, metal deactivators, pour point depressants.

[0076] The total combined amount of the lubricant additive in the lubricant may include ranges of 0-25 wt%, or 0.01-20 wt%, or 0.1-15 wt% or 0.5-10 wt%, or 1-5 wt% of the lubricant.

[0077] The viscosity index improvers include high molecular weight polymers that increase the relative viscosity of an oil at high temperatures more than they do at low temperatures. Viscosity index improvers include polyacrylates, polymethacrylates, alkylmethacrylates, vinylpyrrolidone / meth-acrylate copolymers, poly vinylpyrrolidones, polybutenes, olefin copolymers such as an ethylene-propylene copolymer or a styrene-butadiene copolymer or polyalkene such as PIB, styrene / acrylate copolymers and polyethers, and combinations thereof. The most common VI improvers are methacrylate polymers and copolymers, acrylate polymers, olefin polymers and copolymers, and styrenebutadiene copolymers. Other examples of the viscosity index improver include polymethacrylate, polyisobutylene, alpha-olefin polymers, alpha-olefin copolymers (e.g., an ethylenepropylene copolymer), polyalkylstyrene, phenol condensates, naphthalene condensates, a styrenebutadiene copolymer and the like. Of these, polymethacrylate having a number average molecular weight of 10000 to 300000, and alpha-olefin polymers or alpha-olefin copolymers having a number average molecular weight of 1000 to 30000, particularly ethylene- alpha-olefin copolymers having a number average molecular weight of 1000 to 10000 are preferred. The viscosity index increasing agents can be added and used individually or in the form of mixtures, conveniently in an amount within the range of from ≥ 0.05 to ≤ 20.0 % by weight, in relation to the weight of the base stock.

[0078] Suitable (polymeric) thickeners include, but are not limited to, polyisobutenes (PIB), oligomeric co-polymers (OCPs), polymethacrylates (PMAs), copolymers of styrene and butadiene, or high viscosity esters (complex esters).

[0079] Corrosion inhibitors may include various oxygen-, nitrogen-, sulfur-, and phosphoruscontaining materials, and may include metal-containing compounds (salts, organometallics, etc.) and nonmetal-containing or ashless materials. Corrosion inhibitors may include, but are not limited to, additive types such as, for example, hydrocarbyl-, aryl-, alkyl-, arylalkyl-, and alkylaryl- versions of detergents (neutral, overbased), sulfonates, phenates, salicylates, alcoholates, carboxylates, salixarates, phosphites, phosphates, thiophosphates, amines, amine salts, amine phosphoric acid salts, amine sulfonic acid salts, alkoxylated amines, etheramines, polyetheramines, amides, imides, azoles, diazoles, triazoles, benzotriazoles, benzothiadoles, mercaptobenzothiazoles, tolyltriazoles (TTZ-type), heterocyclic amines, heterocyclic sulfides, thiazoles, thiadiazoles, mercaptothiadiazoles, dimercaptothiadiazoles (DMTD-type), imidazoles, benzimidazoles, dithiobenzimidazoles, imidazolines, oxazolines, Mannich reactions products, glycidyl ethers, anhydrides, carbamates, thiocarbamates, dithiocarbamates, polyglycols, etc., or mixtures thereof.

[0080] Detergents include cleaning agents that adhere to dirt particles, preventing them from attaching to critical surfaces. Detergents may also adhere to the metal surface itself to keep it clean and prevent corrosion from occurring. Detergents include calcium alkylsalicylates, calcium alkylphenates and calcium alkarylsulfonates with alternate metal ions used such as magnesium, barium, or sodium. Examples of the cleaning and dispersing agents which can be used include metal-based detergents such as the neutral and basic alkaline earth metal sulphonates, alkaline earth metal phenates and alkaline earth metal salicylates alkenylsuccinimide and alkenylsuccinimide esters and their borohydrides, phenates, salienius complex detergents and ashless dispersing agents which have been modified with sulphur compounds. These agents can be added and used individually or in the form of mixtures, conveniently in an amount within the range of from ≥ 0.01 to ≤ 1.0 % by weight in relation to the weight of the base stock; these can also be high total base number (TBN), low TBN, or mixtures of high / low TBN.

[0081] Dispersants are lubricant additives that help to prevent sludge, varnish and other deposits from forming on critical surfaces. The dispersant may be a succinimide dispersant (for example N-substituted long chain alkenyl succinimides), a Mannich dispersant, an ester-containing dispersant, a condensation product of a fatty hydrocarbyl monocarboxylic acylating agent with an amine or ammonia, an alkyl amino phenol dispersant, a hydrocarbyl-amine dispersant, a polyether dispersant or a polyetheramine dispersant. In one embodiment, the succinimide dispersant includes a polyisobutylene-substituted succinimide, wherein the polyisobutylene from which the dispersant is derived may have a number average molecular weight of about 400 to about 5000, or of about 950 to about 1600. In one embodiment, the dispersant includes a borated dispersant. Typically, the borated dispersant includes a succinimide dispersant including a polyisobutylene succinimide, wherein the polyisobutylene from which the dispersant is derived may have a number average molecular weight of about 400 to about 5000. Borated dispersants are described in more detail above within the extreme pressure agent description.

[0082] Anti-foam agents may be selected from silicones, polyacrylates, and the like. The amount of anti-foam agent in the lubricant compositions described herein may range from ≥ 0.001 wt.-% to≤ 0.1 wt.-% based on the total weight of the formulation. As a further example, an anti-foam agent may be present in an amount from about 0.004 wt.-% to about 0.008 wt.-%.

[0083] Suitable extreme pressure agent is a sulfur-containing compound. In one embodiment, the sulfur-containing compound may be a sulfurised olefin, a polysulfide, or mixtures thereof. Examples of the sulfurised olefin include a sulfurised olefin derived from propylene, isobutylene, pentene; an organic sulfide and / or polysulfide including benzyldisulfide; bis-(chlorobenzyl) disulfide; dibutyl tetrasulfide; di-tertiary butyl polysulfide; and sulfurised methyl ester of oleic acid, a sulfurised alkylphenol, a sulfurised dipentene, a sulfurised terpene, a sulfurised Diels-Alder adduct, an alkyl sulphenyl N'N- dialkyl dithiocarbamates; or mixtures thereof. In one embodiment, the sulfurised olefin includes a sulfurised olefin derived from propylene, isobutylene, pentene or mixtures thereof. In one embodiment the extreme pressure additive sulfur-containing compound includes a dimercaptothiadiazole or derivative, or mixtures thereof. Examples of the dimercaptothiadiazole include compounds such as 2,5-dimercapto-1,3,4-thiadiazole or a hydrocarbyl-substituted 2,5-dimercapto-1,3,4-thiadiazole, or oligomers thereof. The oligomers of hydrocarbyl-substituted 2,5-dimercapto-1,3,4-thiadiazole typically form by forming a sulfur-sulfur bond between 2,5-dimercapto-1,3,4-thiadiazole units to form derivatives or oligomers of two or more of said thiadiazole units. Suitable 2,5-dimercapto-1,3,4-thiadiazole derived compounds include for example 2,5-bis(tert-nonyldithio)-1,3,4-thiadiazole or 2-tert-nonyldithio-5-mercapto-1,3,4-thiadiazole. The number of carbon atoms on the hydrocarbyl substituents of the hydrocarbyl-substituted 2,5-dimercapto-1,3,4-thiadiazole typically include 1 to 30, or 2 to 20, or 3 to 16. Extreme pressure additives include compounds containing boron and / or sulfur and / or phosphorus. The extreme pressure agent may be present in the lubricant compositions at 0 wt.-% to about 20 wt.-%, or at about 0.05 wt.-% to about 10.0 wt.-%, or at about 0.1 wt.-% to about 8 wt.-% of the lubricant composition.

[0084] Examples of anti-wear additives include organo borates, organo phosphites such as didodecyl phosphite, organic sulfur-containing compounds such as sulfurized sperm oil or sulfurized terpenes, zinc dialkyl dithiophosphates, zinc diaryl dithiophosphates, phosphosulfurized hydrocarbons and any combinations thereof.

[0085] Friction modifiers may include metal-containing compounds or materials as well as ashless compounds or materials, or mixtures thereof. Metal-containing friction modifiers include metal salts or metal-ligand complexes where the metals may include alkali, alkaline earth, or transition group metals. Such metal-containing friction modifiers may also have low-ash characteristics. Transition metals may include Mo, Sb, Sn, Fe, Cu, Zn, and others. Ligands may include hydrocarbyl derivative of alcohols, polyols, glycerols, partial ester glycerols, thiols, carboxylates, carbamates, thiocarbamates, dithiocarbamates, phosphates, thiophosphates, dithiophosphates, amides, imides, amines, thiazoles, thiadiazoles, dithiazoles, diazoles, triazoles, and other polar molecular functional groups containing effective amounts of O, N, S, or P, individually or in combination. In particular, Mo-containing compounds can be particularly effective such as for example Mo-dithiocarbamates, Mo(DTC), Mo-dithiophosphates, Mo(DTP), Mo-amines, Mo (Am), Mo-alcoholates, Mo- alcohol-amides, and the like.

[0086] Ashless friction modifiers may also include lubricant materials that contain effective amounts of polar groups, for example, hydroxyl-containing hydrocarbyl base oils, glycerides, partial glycerides, glyceride derivatives, and the like. Polar groups in friction modifiers may include hydrocarbyl groups containing effective amounts of O, N, S, or P, individually or in combination. Other friction modifiers that may be particularly effective include, for example, salts (both ashcontaining and ashless derivatives) of fatty acids, fatty alcohols, fatty amides, fatty esters, hydroxyl-containing carboxylates, and comparable synthetic long-chain hydrocarbyl acids, alcohols, amides, esters, hydroxy carboxylates, and the like. In some instances, fatty organic acids, fatty amines, and sulfurized fatty acids may be used as suitable friction modifiers. Examples of friction modifiers include fatty acid esters and amides, organo molybdenum compounds, molybdenum dialkylthiocarbamates and molybdenum dialkyl dithiophosphates.

[0087] Suitable metal deactivators include benzotriazoles and derivatives thereof, for example 4- or 5-alkylbenzotriazoles (e.g. triazole) and derivatives thereof, 4,5,6,7-tetrahydrobenzotriazole and 5,5'-methylenebisbenzotriazole; Mannich bases of benzotriazole or triazole, e.g. 1-[bis(2-ethylhexyl) aminomethyl) triazole and 1-[bis(2- ethylhexyl) aminomethyl)benzotriazole; and alkoxyalkylbenzotriazoles such as 1-(nonyloxymethyl)benzotriazole, 1-(1-butoxyethyl) benzotriazole and 1-(1-cyclohexyloxybutyl) triazole, and combinations thereof. Additional non-limiting examples of the one or more metal deactivators include 1,2,4-triazoles and derivatives thereof, for example 3-alkyl(or aryl)-1, 2,4-triazoles, and Mannich bases of 1,2,4-triazoles, such as 1-[bis(2-ethylhexyl) aminomethy1-1, 2,4-triazole; alkoxyalky1-1, 2,4-triazoles such as 1-(1-butoxyethyl)-1, 2,4-triazole; and acylated 3-amino-1, 2,4-triazoles, imidazole derivatives, for example 4,4'-methylenebis(2-undecyl-5-methylimidazole) and bis[(N-methyl)imidazol-2-yl]-carbinol octyl ether, and combinations thereof. Further non-limiting examples of the one or more metal deactivators include sulfur-containing heterocyclic compounds, for example 2-mercaptobenzothiazole, 2,5-dimercapto-1, 3,4-thia-diazole and derivatives thereof; and 3,5-bis[di(2-ethylhexyl) aminomethyl]-1, 3,4-thiadiazolin-2-one, and combinations thereof. Even further non-limiting examples of the one or more metal deactivators include amino compounds, for example salicylidenepropylenediamine, salicylami-noguanidine and salts thereof, and combinations thereof. The one or more metal deactivators are not particularly limited in amount in the composition but are typically present in an amount of from about 0.01 to about 0.1, from about 0.05 to about 0.01, or from about 0.07 to about 0.1, wt.-% based on the weight of the composition. Alternatively, the one or more metal deactivators may be present in amounts of less than about 0.1, of less than about 0.7, or less than about 0.5, wt.-% based on the weight of the composition.

[0088] Pour point depressants (PPD) include polymethacrylates, alkylated naphthalene derivatives, and combinations thereof. Commonly used additives such as alkylaromatic polymers and polymethacrylates are also useful for this purpose. Typically, the treat rates range from ≥ 0.001 wt.-% to ≤ 1.0 wt.-%, in relation to the weight of the base stock.

[0089] Demulsifiers include trialkyl phosphates, and various polymers and copolymers of ethylene glycol, ethylene oxide, propylene oxide, or mixtures thereof.

[0090] The invention also relates to a method for lubricating a mechanical device in an electric vehicle comprising the step of contacting the lubricant with the mechanical device.

[0091] Suitable electric vehicles are fully electric vehicles and hybrid electric vehicles. An electric vehicle usually comprises a rotary electric machine and an electric power storage device configured to store electric power that is used to drive the rotary electric machine. A hybrid electric vehicle usually travels by using power of a rotary electric machine and a combustion engine.

[0092] Suitable hybrid electric vehicles are full hybrid (also called strong hybrid), plug-in hybrid (also called PHEV) electric vehicles, or range extended electric vehicles (also called REEV). A full hybrid electric vehicle is typically a vehicle that can run only on a combustion engine, only on an electric motor, or a combination of both. A plug-in hybrid electric vehicle is typically a hybrid electric vehicle with rechargeable batteries that can be restored to full charge by connecting a plug to an external electric power source.

[0093] Suitable electric vehicles are battery electric vehicles (also called BEV) or fuel cell electric vehicles. A BEV is typically a type of electric vehicle that uses chemical energy stored in rechargeable battery packs, and uses electric motors and motor controllers instead of internal combustion engines for propulsion. A fuel cell electric vehicle (FCEV) is typically a type of electric vehicle which uses a fuel cell, instead of a battery, or in combination with a battery or supercapacitor, to power its on-board rotary electric machine. Fuel cells in vehicles generate electricity to power the motor, generally using oxygen from the air and compressed hydrogen.

[0094] The term "vehicle" refers to any mobile or stationary platform, wherein mobile platforms are preferred. In particular vehicles are selected from a passenger vehicle, a light-duty or heavyduty truck, a utility vehicle, an agricultural vehicle, an industrial or warehouse vehicle, or a recreational off-road vehicle.

[0095] The lubrication of a mechanical device in an electric vehicles may refer to lubrication of powertrains, drivelines, transmissions, differentials, gears, gear trains, gear sets, gear boxes, bearings, bushings, axles, turbines, compressors, pumps, hydraulic systems, batteries, capacitors, electric motors, drive motors, generators, AC / DC converters, alternators, transformers, kinetic energy converters, kinetic energy recovery systems. A single lubricant or more than one lubricant may be used in the electric vehicle, for example, one lubricant composition for the transmission and another lubricant composition for another component of the vehicle system.

[0096] The invention also relates to a use of the alkoxylated alcohol for increasing the breakdown voltage of the lubricant comprising a basestock selected from the hydrocarbons.

[0097] Preferably, the breakdown voltage of the lubricant comprising the alkoxylated alcohol is at least 100, 500, 1000, 2000, or 5000 V higher compared to the lubricant without the alkoxylated alcohol.

[0098] Preferably, the use of the alkoxylated alcohol for increasing the breakdown voltage of the lubricant comprising the base stock selected from the hydrocarbons is in an electric vehicle.

[0099] The invention also relates to a use of the alkoxylated alcohol in the lubricant comprising the base stock selected from the hydrocarbons for reducing the electric discharge machining.Examples

[0100] Base Stock A: API Group III base stock, YUBASE 3 from SK Lubricants Ltd, clear liquid hydrocarbons, mineral oil, kinematic viscosity (ASTM D445) at 40 °C 12,4 mm 2< / s, at 100 °C 3,1 mm 2< / s, viscosity index 112 (ASTM D2270), sulfur content <10 ppm (ASTM D2622). Base Stock B: API Group III base stock, YUBASE 6 from SK Lubricants Ltd, clear liquid hydrocarbons, mineral oil, kinematic viscosity (ASTM D445) at 40 °C 36,8 mm 2< / s, at 100 °C 6,5 mm 2< / s, viscosity index 131 (ASTM D2270), sulfur content <10 ppm (ASTM D2622). Additives Pack: An additives package was added comprising commercial additives of the classes of antioxidants, antiwear additive, corrosion inhibitor, metal deactivator, silicon oil. Polyalphaolefin 150: a highly branched isoparaffinic polyalphaolefin, kinematic viscosity at 40 °C 1719 mm 2< / s, at 100 °C 156 mm 2< / s, Synfluid mPAO 150 cST from Chevron Phillips. Polymethylacrylate: a polyalkyl methacrylate viscosity index improver, with linear and branched C 12-15 alkyl groups, permanent shear stability index about 20 (20 h KRL; determined according CEC L-45-99). Alkoxylate A: a liquid alkoxylated alcohol, where the alcohol was polytetrahydrofuran (mol weight about 650 g / mol) which was randomly alkoxylated with 12 equivalents of dodecyl epoxide and 20 equivalents of proyplene oxide, kinematic viscosity (ASTM D445) at 40 °C about 320-350 mm 2< / s Example 1

[0101] The lubricants A, B, and C were prepared from the Base Stock A, the Additives Pack (1.1 wt% concentration) and either the Base Stock B, the Polymethylacrylate (comparative), the Polyalphaolefin 150 (comparative), or the Alkoxylate A with the amount given in Table 1. The amounts of the the Base Stock B, the Polymethylacrylate, the Polyalphaolefin 150, and the Alkoxylate A were adjusted to achieve a KV100 of 5 mm 2< / s in the final lubricant.

[0102] The kinematic viscosity at 40 °C (KV40) and at 100 °C (KV100) was determined according to ASTM D445. The viscosity index VI was calculated from these data. The water content of the final lubricant was determined by the Karl Fischer method (DIN 517771 / ASTM D 1744). The breakdown voltage of the final lubricant was determined by DIN EN 60156 ("Insulating liquids - Determination of the breakdown voltage at power frequency - Test method").

[0103] The results are summarized in Table 1 and demonstrate for Lubricant E an increased breakdown voltage. A high breakdown voltage is advantageous because the lubricant acts as an insulator.

[0104] The comparative Lubricant A has a very low water content of 20 ppm. Typically, in hydrocarbons with low water content the breakdown voltage increases, as can also be obseved comparing comparative Lubricants C and D. Surprisingly Lubricant E has a higher breakdown voltage although it has a higher water content of 300 ppm. Table 1Lubricant A a< ) B a< ) C a< ) D a< ) E Base Stock A88.0 %83.6 %32.932.980.8 %Base Stock B--66.066.0-Polymethylacrylate10.9 %----Polyalphaolefin 150-15.3 %---Alkoxylate A----18.1 %KV40 [mm 2< / s]20.922.224.524.521.9KV100 [mm 2< / s]5.05.0555.0VI179181132132166Water content20 ppm58 ppm85 ppm151 ppm300 ppmBreakdown voltage24 kV30 kV35 kV23 kV56 kVa) Comparative example Example 2

[0105] The EDM (electric discharge machining) currents of Lubricants A, B and E from Example 1 were analyzed on a test rig where a common mode voltage was applied to a rotating bearing while the resulting bearing currents were recorded according to R. Pelz et al. "Charakterisierung von E-Fluiden von der Laboranalytik bis zum Prüfstand", MTZ - Motorentechnische Zeitschrift, 2021 (10), 46-50. The temperature was varied from 30 to 80 °C and the common mode voltage varied between 5, 10, and 20 Volt.

[0106] The results are summarized in Table 2 and demonstrate for Lubricant E a reduced total EDM currents. A reduced total EDM current is advantageous because the EDM currents result in damage of the bearings.

[0107] Table 2: EDM currents [1 / s] are bold, ohmic currents [1 / s] are italic. Lubricant30°C40°C50°C5V10V20V5V10V20V5V10V20VA06486 5612903 1056 011722 1530B14208 1931 149278 2805389 280E7292 002528 002361 00 Table 2 (continued) 60°C70°C80°CLubricant5V10V20V5V10V20V5V10V20Vtotal EDM currentsA8944 005264 1405000 0051375 B6153 9707764 37508708 361053431 E3890028004440012181

Claims

1. A method for lubricating a mechanical device in an electric vehicle comprising the step of contacting the lubricant with the mechanical device, where the lubricant comprises - a base stock selected from hydrocarbons, - 50 to 600 ppm water, and - an alkoxylated alcohol, where the alcohol is a polytetrahydrofuran with 5 to 20 repeating units, and where the alcohol is alkoxylated with a hydrophobic epoxide which is dodecyl oxide, and where the lubricant comprises 5 to 30 wt% of the alkoxylated alcohol.

2. The method according to claim 1 where the alcohol is alkoxylated with the hydrophobic epoxide and in addition with propylene oxide.

3. The method according to claim 1 or claim 2 where the lubricant comprises 10 to 25 wt%, of the alkoxylated alcohol.

4. The method according to any of claims 1 to 3 where the hydrocarbons are selected from API Groups I, II, III or IV base stocks, or mixtures thereof.

5. The method according to any of claims 1 to 4 where the lubricant is free from API Group V base stocks.

6. The method according to any of claims 1 to 5 where the base stock has a breakdown voltage of up to 500 Volt.

7. The method according to any of claims 1 to 6 where the alkoxylated alcohol is an alkoxylated polytetrahydrofuran of general formula (I) wherein m is an integer in the range of ≥ 1 to ≤ 25, m' is an integer in the range of ≥ 1 to ≤ 25, (m+m') is an integer in the range of ≥ 3 to ≤ 50, n is an integer in the range of ≥ 0 to ≤ 45, n' is an integer in the range of ≥ 0 to ≤ 45, (n+n') is an integer in the range of ≥ 0 to ≤ 80, p is an integer in the range of ≥ 5 to ≤ 20, p' is an integer in the range of ≥ 5 to ≤ 20, k is an integer in the range of ≥ 5 to ≤ 20, R1 denotes an unsubstituted, linear or branched, alkyl radical having 10 carbon atoms, R2 denotes -CH2-CH3, and R3 denotes-CH3, whereby the concatenations denoted by k are distributed to form a block polymeric structure and the concatenations denoted by p, p', n, n', m and m' are distributed to form a block polymeric structure or a random polymeric structure, wherein the ratio of (m+m') to k is in the range of 0.3:1 to 4:1 and the ratio of (p+p') to k it is in the range of 1.5:1 to 5:1.

8. A lubricant as defined in the preceeding claims comprising - a base stock selected from hydrocarbons which are selected from API Groups I, II, or III base stocks, - 50 to 600 ppm water, and - an alkoxylated alcohol, where the alcohol is a polytetrahydrofuran with 5 to 20 repeating units, and where the alcohol is alkoxylated with a hydrophobic epoxide which is dodecyl oxide, and where the lubricant comprises 5 to 30 wt% of the alkoxylated alcohol.

9. A use of an alkoxylated alcohol for increasing the breakdown voltage of a lubricant comprising the basestock selected from the hydrocarbons, wherein the lubricant comprises 50 to 600 ppm water, and where the lubricant comprises 5 to 30 wt% of the alkoxylated alcohol, and where the alcohol is a polytetrahydrofuran with 5 to 20 repeating units, and where the alcohol is alkoxylated with a hydrophobic epoxide which is dodecyl oxide.

10. A use of an alkoxylated alcohol in a lubricant comprising the base stock selected from the hydrocarbons for reducing the electric discharge machining, wherein the lubricant comprises 50 to 600 ppm water, and where the lubricant comprises 5 to 30 wt% of the alkoxylated alcohol, and where the alcohol is a polytetrahydrofuran with 5 to 20 repeating units, and where the alcohol is alkoxylated with a hydrophobic epoxide which is dodecyl oxide.