Tetrahydrobenzotriazole for improving an Anti-corrosion property in electric vehicles

Abstract

The present invention relates to a use of a tetrahydrobenzotriazole of the formula (I) for improving an anti-corrosion property of an automotive fluid selected from a lubricant or a coolant in a propulsion system of an electric vehicle. The invention also relates to a method for improving an anti-corrosion properties of an automotive fluid selected from a lubricant or a coolant in a propulsion system of an electric or hybrid vehicle comprising the step of adding the tetrahydrobenzotriazole of the formula (I) to the lubricant or the coolant.

Description

[0001] Tetrahydrobenzotriazole for improving an anti-corrosion property in electric vehicles

[0002] The present invention relates to a use of a tetrahydrobenzotriazole of the formula (I) for improving an anti-corrosion property of an automotive fluid selected from a lubricant or a coolant in a propulsion system of an electric vehicle. The invention also relates to a method for improving an anti-corrosion properties of an automotive fluid selected from a lubricant or a coolant in a propulsion system of an electric or hybrid vehicle comprising the step of adding the tetrahydrobenzotriazole of the formula (I) to the lubricant or the coolant.

[0003] Corrosion protection in electric vehicles is an important topic, especially the corrosion protection of the propulsion system. There is an ongoing need to improve lubricants or coolants in this regard.

[0004] The object was solved by a use of a tetrahydrobenzotriazole of the formula (I) for improving an anti-corrosion property of an automotive fluid selected from a lubricant or a coolant in a propulsion system of an electric vehicle.

[0005] The object was also solved by a method for improving an anti-corrosion properties of an automotive fluid selected from a lubricant or a coolant in a propulsion system of an electric or hybrid vehicle comprising the step of adding the tetrahydrobenzotriazole of the formula (I) to the lubricant or the coolant. The tetrahydrobenzotriazole of the formula (I) is commercially available.

[0006] The tetrahydrobenzotriazole can be present in dissolved, suspended or emulsified form in the automotive fluid. The tetrahydrobenzotriazole is preferably present in dissolved form in the automotive fluid.

[0007] The automotive fluid comprises usually comprises 0.0001 to 1.0 wt%, preferably 0.0002 to 0.2 wt%, and in particular 0.0005 to 0.08 wt% of the tetrahydrobenzotriazole.

[0008] The automotive fluid selected from lubricants usually comprises 0.0001 to 1 .0 wt%, preferably 0.0002 to 0.2 wt%, and in particular 0.02 to 0.5 wt% of the tetrahydrobenzotriazole.

[0009] The automotive fluid selected from coolants usually comprises usually 0.0001 to 1 .0 wt%, preferably 0.0002 to 0.2 wt%, and in particular 0.0005 to 0.08 wt% of the tetra hyd ro be nzotri azo I e .

[0010] The anti-corrosion property is usually improved towards a nonferrous metal, such as copper or a copper-containing alloy. The nonferrous metal is preferably copper or a copper-containing alloy.

[0011] The improvement of the anti-corrosion property can be evaluated by means of a test involving study of the breakdown time of a test compound (e.g. a copper wire of a preestablished diameter (e.g. 60 pm)) under a small current at elevated temperature in the automotive fluid

[0012] (preferably the lubricant). The improvement of the anti-corrosion property may also be evaluated by a test involving the determination of the corrosion current.

[0013] The improvement of the automotive fluid is usually determined in comparison to the same automotive fluid, but without the tetrahydrobenzotriazole.

[0014] 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.

[0015] Suitable hybrid electric vehicles are full hybrid (sometimes also called strong hybrid), plug-in hybrid (also called PH EV) electric vehicles, or range extended electric vehicles (sometimes 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.

[0016] 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.

[0017] 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 heavy- duty truck, a utility vehicle, an agricultural vehicle, an industrial or warehouse vehicle, or a recreational off-road vehicle.

[0018] In one form the lubricant is present within the rotary electric machine of the electric vehicle.

[0019] In another form the lubricant is present outside in close distance to the rotary electric machine of the electric vehicle, and usually onboard of the electric vehicle. Preferably, the lubricant is present outside the rotary electric machine in direct contact with it or within a distance of up to 300, 250, 200, 150, 100, 50, 40, 30, 20 or 10 cm. Examples for the lubricant being present outside the rotary electric machine are lubricants present in powertrains, drivelines, transmissions, differentials, gears, gear trains, gear sets, gear boxes, bearings, bushings, axles, turbines, compressors, pumps, hydraulic systems, batteries, capacitors, generators, AC / DC converters, alternators, transformers, kinetic energy converters, or kinetic energy recovery systems.

[0020] The propulsion system is usually a system comprising the mechanical parts required for propelling the electric vehicle, such as an electric motor, comprising the rotor-stator assembly of the power electronics (dedicated to regulating the speed), a transmission and a battery. In one form the automotive fluid is selected from the lubricant. Preferably, the automotive fluid is selected from the lubricant.

[0021] The lubrication of 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.

[0022] The lubricant may lubricate various surfaces of electric vehicles, that include, for example, the following: metals, metal alloys, non-metals, non-metal alloys, mixed carbon-metal composites and alloys, mixed carbon-nonmetal composites and alloys, ferrous metals, ferrous composites and alloys, non-ferrous metals, non-ferrous composites and alloys, titanium, titanium composites and alloys, aluminum, aluminum composites and alloys, magnesium, magnesium composites and alloys, ion-implanted metals and alloys, plasma modified surfaces; surface modified materials; coatings; mono-layer, multi-layer, and gradient layered coatings; honed surfaces; polished surfaces; etched surfaces; textured surfaces; micro and nano structures on textured surfaces; super-finished surfaces; diamond-like carbon (DLC), DLC with high-hydrogen content, DLC with moderate hydrogen content, DLC with low-hydrogen content, DLC with nearzero hydrogen content, DLC composites, DLC-metal compositions and composites, DLC- nonmetal compositions and composites; ceramics, ceramic oxides, ceramic nitrides, FeN, CrN, ceramic carbides, mixed ceramic compositions, cermets, and the like; polymers, thermoplastic polymers, engineered polymers, polymer blends, polymer alloys, polymer composites; materials compositions and composites containing dry lubricants, that include, for example, graphite, carbon, molybdenum, molybdenum disulfide, polytetrafluoroethylene, polyperfiuoropropylene, polyperfluoroalkylethers, and the like; super hydrophobic surfaces; super hydrophilic surfaces; self-healing surfaces; surfaces derived from 3-D printing or additive manufacturing techniques, which may be additionally used as -manufactured, or used with post-printing surface finishing, or used with post-printing surface coating.

[0023] The term “lubricants” usually refers to composition which are 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.

[0024] The lubricant usually further comprises in addition to the tetrahydrobenzotriazole

[0025] - a base oil selected from mineral oils, polyalphaolefins, polymerized and interpolymerized olefins, alkyl naphthalenes, alkylene oxide polymers, silicone oils, phosphate ester; and / or

[0026] - a lubricant additive.

[0027] The base oil may selected from the group consisting of mineral oils (Group I, II or III oils), polyalphaolefins (Group IV oils), polymerized and interpolymerized olefins, alkyl naphthalenes, alkylene oxide polymers, silicone oils, phosphate esters (Group V oils). Preferably, the further base oil is selected from Group I, Group II, Group III base oils according to the definition of the API, or mixtures thereof. Definitions for the base oils are the same as those 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. Further Group V base oils are carboxylic acid ester, such as monoester, diester, polyester, complex ester, or mixtures thereof.

[0028] Synthetic base oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and interpolymerized olefins (e.g., polypropylenes, propylene-isobutylene copolymers, chlorinated polybutylenes, poly(1 -hexenes), poly(1 -octenes), poly(1 -decenes)); alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)benzenes); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenols); and alkylated diphenyl ethers and alkylated diphenyl sulfides and derivative, analogs and homologs thereof.

[0029] Alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, etc., constitute another class of known synthetic base oils. These are exemplified by polyoxyalkylene polymers prepared by polymerization of ethylene oxide or propylene oxide, and the alkyl and aryl ethers of polyoxyalkylene polymers (e.g., methyl-polyisopropylene glycol ether having a molecular weight of 1000 or diphenyl ether of polyethylene glycol having a molecular weight of 1000 to 1500); and mono- and polycarboxylic esters thereof, for example, the acetic acid esters, mixed C3-C8 fatty acid esters and C13 oxo acid diester of tetraethylene glycol.

[0030] Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy- or polyaryloxysilicone oils and sili-cate oils comprise another useful class of synthetic base oils; such base oils include tetraethyl silicate, tetraisopropyl silicate, tetra-(2- ethylhexyl)silicate, tetra-(4-methyl-2-ethyl- hexyl) silicate, tetra-(p-tert-butyl-phenyl) silicate, hexa-(4-methyl-2-ethylhexyl)disiloxane, poly(methyl) siloxanes and poly(methylphenyl)siloxanes. Other synthetic base oils include liquid esters of phosphorous-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, diethyl ester of decylphosphonic acid) and polymeric tetrahydrofurans.

[0031] Suitable carboxylic acid esters are obtainable by reacting

[0032] (i) at least one linear or branched C2-C24 monocarboxylic acid with at least one linear or branched C1-C20 monoalcohol (also called “monoester”) or; (ii) at least one linear or branched C2-C20 dicarboxylic acid with at least one linear or branched C1-C20 monoalcohol (also called “diester”)or;

[0033] (iii) at least one linear or branched C2-C24 monocarboxylic acid with at least one C2-C20 polyol having 2-10 hydroxyl group (also called “polyester”)or;

[0034] (iv) a mixture comprising at least one linear or branched C2-C24 monocarboxylic acid and at least one linear or branched C2-C20 dicarboxylic acid and at least one C2-C20 polyol having 2-10 hydroxyl group (also called “complex ester”) or;

[0035] (v) at least one linear or branched C2-C20 dicarboxylic acid with at least one C2-C20 polyol having 2-10 hydroxyl group or;

[0036] (vi) a mixture comprising at least one linear or branched C2-C24 monocarboxylic acid and at least one linear or branched C2-C20 dicarboxylic acid and at least one linear or branched Ci- 020 monoalcohol or;

[0037] (vii) a mixture comprising at least one linear or branched C2-C24 monocarboxylic acid and at least one linear or branched C2-C20 dicarboxylic acid and at least one C2-C20 polyol having 2-10 hydroxyl group and at least one C1-C20 monoalcohol.

[0038] In one form the carboxylic acid ester is a monoester obtainable by reacting

[0039] - at least one linear or branched C5-C20 monocarboxylic acid selected from the group consisting of pentanoic acid, iso-pentanoic acid, hexanoic acid, iso-hexanoic acid, heptanoic acid, iso-heptanoic acid, octanoic acid, iso-octanoic acid, nonanoic acid, iso-nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, nonadecanoic acid, eicosanoic acid with

[0040] - at least one linear or branched C1-C18 monoalcohol selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, 1 -octanol, 3-methyl-1- butanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, iso-propanol, iso-butanol, 2-octanol, 3-octanol, iso- nonanol, iso-decanol, iso-undecanol, iso-dodecanol iso-tride-canol, iso-tetradecanol, isopentadecanol, iso-hexadecanol, iso-heptadecanol, iso-octadecanol, neo-pentanol , t-butanol, 2-methyl-2-butanol, 2,3-dimethyl-2-butanol, 2-methyl-2-pentanol, 3-methyl-3-pentanol, 3- ethyl-3-pentanol, 2,3-dimethyl-2-pentanol, 2,3-dimethyl-2-pentanol, 2,3-dimehtyl-2-pentanol, 2,3-dimethyl-3-pentaol, 2,3,4-tri-methyl-3-pentanol, 2-methyl-2-hexanol and 3-methyl-3- hexanol.

[0041] In another form the monoester is obtainable by reacting at least one linear or branched C12-C20 monocarboxylic acid with at least one linear or branched Ce-Cie monoalcohol. In another form the monoester is obtainable by reacting at least one linear or branched C14-C18 monocarboxylic acid with at least one linear or branched C6-C12 monoalcohol. Examples for monosters are 2- ethylhexyl oleate, 2-ethylhexyl cocoate, 2-ethylhexyl palmitate, 2-ethylhexylstearate, and 2- ethylhexyl tallowate.

[0042] In another form the carboxylic acid ester is a diester obtainable by reacting

[0043] - at least one linear or branched C3-C12 dicarboxylic acid selected from the group consisting of malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, azelaic acid, sebacic acid, brassilic acid, docdecanedioic acid, diglycolic acid, 1 ,4-cyclohexanedicarboxylic acid, 1 ,3-cyclohexanedicarboxylic acid and 2,6-decahydro-naphthalenedicarboxylic acid with

[0044] - at least one branched C5-C14 monoalcohol selected from the group consisting of pentanol, hexanol, heptanol, iso-pentanol, iso-hexanol, iso-heptanol, 2-ethylhexanol, 2-propylheptanol, 2-propyl-4-methyl-hexanol, 2-propyl-5-methyl-hexanol, 2-isopropyl-4- methyl-hexanol, 2-isopropyl-5-methyl-hexanol, 2-propyl-4,4-dimethylpentanol, 2-ethyl-2,4- dimethylhexanol, 2-ethyl-2-methyl-heptanol, 2-ethyl-2,5-dimethylhexanol, 2-iso-propyl- heptanol, 2-butyl-1 -octanol and 2-pentyl-1 -nonanol.

[0045] In one form the diesters are obtainable by reacting at least one linear or branched C4-C8 dicarboxylic acid with at least one branched Ce-Ci6 monoalcohol. In one form the diesters are obtainable by reacting at least one linear or branched Ce-Cs dicarboxylic acid with at least one branched C3-Ci4monoalcohol. Examples for diesters are diisodecyl adipate, diisotridecyl adipate, di-(isopropylheptyl)-adipate (DPHA) and diisononyladipate (DNA).

[0046] Preferably, the lubricant comprises a base oil selected from Group III mineral oil, polyalphaolefins, or esters.

[0047] In a preferred form the lubricant comprises a base oil selected from Group III mineral oil. In another preferred form the lubricant comprises a base oil selected from polyalphaolefins. In another preferred form the lubricant comprises a base oil selected from esters.

[0048] 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, pour point depressants.

[0049] 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 FIB, 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 alphaolefin 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.

[0050] 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).

[0051] Corrosion inhibitors may include various oxygen-, nitrogen-, sulfur-, and phosphorus-containing 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.

[0052] 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.

[0053] 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.

[0054] 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.-%.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] In addition to the tetrahydrobenzotri azole the lubricant may comprise a metal deactivator.

[0060] Suitable metal deactivators include benzotriazoles and derivatives thereof, for example 4- or 5- alkylbenzotriazoles (e.g. triazole) and derivatives thereof, 5,5'-methylenebisbenzotriazole; Mannich bases of benzotriazole or triazole, e.g. 1-[bis(2-ethyl-hexyl) aminomethyl) triazole and 1-[bis(2- ethylhexyl) aminomethyl)benzotriazole; and alkoxy-alkylbenzotriazoles 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) aminomethyl -1 ,

[0061] 2.4-triazole; alkoxyalkyl -1 , 2,4-triazoles such as 1-(1-bu-toxyethyl)-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-mercapto-benzothiazole, 2,5-dimercapto-1 ,

[0062] 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.

[0063] 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.

[0064] Demulsifiers include trialkyl phosphates, and various polymers and copolymers of ethylene glycol, ethylene oxide, propylene oxide, or mixtures thereof. The electrical conductivity of the automotive fluid may be at least 0.01 , 0.1 , 0.5, 1 , 5, 10, 30, 50, or 100 pS / m.

[0065] The electrical conductivity of the automotive fluid may be up to 100 000, 50 000, 10 000, 5000, 1000, or 500 pS / m.

[0066] The The electrical conductivity of the automotive fluid may be in the range from 0.1 to 100 000 pS / m, 1 to 50 000 pS / m, 1 to 10 000 pS / m, 10 to 5000 pS / m, 10 to 1000 pS / m, 10 to 500 pS / m or 30 to 300 pS / m.

[0067] The electrical conductivity may be determined preferably according to ASTM D2624 “Standard Test Methods for Electrical Conductivity of Aviation and Distillate Fuels”, typically at 25 °C. In another form the electrical conductivity may be determined according to ASTM D4308 „Standard Test Method for Electrical Conductivity of Liquid Hydrocarbons by Precision Meter”, typically at 25 °C.

[0068] In another form the automotive fluid is selected from the coolant.

[0069] The coolant can be prepared from antifreeze concentrates with ion-free water to make ready-to- use aqueous coolants. The coolant may comprise

[0070] - from 10 to 90% by weight of alkylene glycols or derivatives thereof,

[0071] - from 90 to 10% by weight of water, and

[0072] - optionally coolant additives.

[0073] The sum of all components in the coolant is usually 100% by weight. The preferred mixing ratio by weight between the alkylene glycol or derivatives thereof and water in the coolant is from 20:80 to 80:20, in particular from 25:75 to 75:25, preferably from 65:35 to 35:65, especially from 60:40 to 40:60.

[0074] The alkylene glycol component or derivative thereof, it is possible to use, in particular, monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and mixtures thereof, but also monopropylene glycol, dipropylene glycol and mixtures thereof, 1 ,3- propanediol, higher poly alkylene glycols, alkylene glycol ethers, for example monoethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, monoethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, monoethylene glycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether and tetraethylene glycol mono-n-butyl ether, or glycerol, in each case either alone or as mixtures thereof.

[0075] The water used for the coolant can be ion-free, may have a neutral pH-value and comprising essentially no further ions than those hydroxide ions and hydronium ions out of the autoprotolysis of water at the respective temperature. The electrical conductivity (throughout this text determined according to ASTM D 1125) at 25 °C of the ion-free water used should preferably not exceed 5 pS / cm, more preferably not more than 3, even more preferably not more than 2, and especially not more than 1 pS / cm.

[0076] The coolant may have an initial electrical conductivity of at most 50 |iS / cm, in particular 25 |iS / cm, preferably 10 |iS / cm, especially 5 |iS / cm. The conductivity is usually kept at this low level in long-term operation of the propulsion system over a number of weeks or months, in particular if a cooling system with integrated ion exchanger is used.

[0077] The pH of the coolant is usually in the range from 4.5 to 7 in the case of fresh coolant and usually drops to 3.5 in long-term operation. The ion-free water used for the dilution may be pure distilled or bidistilled water or water that has been deionized by, for example, ion exchange.

[0078] The coolants may further comprise at least one aliphatic, cycloaliphatic or aromatic monocarboxylic, dicarboxylic or tricarboxylic acid in the form of alkali metal, ammonium or substituted ammonium salts thereof having from 3 to 21 carbon atoms in the acid part.

[0079] Aliphatic, cycloaliphatic or aromatic, preferably aliphatic or aromatic, and very preferably aliphatic monocarboxylic acids having in each case from 3 to 16 carbon atoms in the form of their alkali metal, ammonium or substituted ammonium salts;

[0080] Aliphatic or aromatic dicarboxylic or tricarboxylic acids, preferably dicarboxylic acids having in each case from 3 to 21 carbon atoms in the form of their alkali metal, ammonium or substituted ammonium salts.

[0081] Possible linear or branched aliphatic or cycloaliphatic, preferably aliphatic monocarboxylic acids of group are, for example, propionic acid, pentanoic acid, hexanoic acid, cyclohexylacetic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, isononanoic acid, decanoic acid, neodecanoic acid, undecanoic acid or dodecanoic acid. Suitable aromatic monocarboxylic acids of group are in particular benzoic acid and also, for example, Ci-Cs-alkylbenzoic acids such as o-, m- or p-methylbenzoic acid or p-tert-butylbenzoic acid, hydroxyl-com prising aromatic monocarboxylic acids such as o-, m- or p-hydroxybenzoic acid or p-(hydroxymethyl)benzoic acid or halobenzoic acids such as o-, m- or p-fluorobenzoic acid.

[0082] As used herein, isononanoic acid refers to one or more branched-chain aliphatic carboxylic acids with 9 carbon atoms. Embodiments of isononanoic acid used in the engine coolant composition may include 7-methyloctanoic acid (e.g., CAS Nos. 693-19-6 and 26896-18-4), 6,6- dimethylheptanoic acid (e.g., CAS No. 15898-92-7), 3,5,5-trimethylhexanoic acid (e.g., CAS No. 3302-10-1), 3,4,5-trimethylhexanoic acid, 2,5,5-trimethylhexanoic acid, 2, 2,4,4- tetramethylpentanoic acid (e.g., CAS No. 3302-12-3) and combinations thereof. In a preferred embodiment, isononanoic acid has as its main component greater than 90% of one of 7- methyloctanoic acid, 6,6-dimethylheptanoic acid, 3,5,5-trimethylhexanoic acid, 3,4,5- trimethylhexanoic acid, 2,5,5-trimethylhexanoic acid, and 2,2,4,4-tetramethylpentanoic acid. The balance of the isononanoic acid may include other nine carbon carboxylic acid isomers and minor amounts of one or more contaminants. In a preferred embodiment, the isononanoic acid has as its main component greater than 90% of 3,5,5-trimethylhexanoic acid and even more preferably, the main component is greater than 95% 3,5,5-trimethylhexanoic acid. Preferred are 2-ethylhexanoic acid and isononanoic acid

[0083] Typical examples of dicarboxylic or tricarboxylic acids, preferably dicarboxylic acids, more preferably aliphatic dicarboxylic acids of group are malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid (decanedioic acid), undecanedioic acid, dodecanedioic acid, cyclopentadienedicarboxylic acid, terephthalic acid, phthalic acid and triazinetriiminocarboxylic acids such as 6,6',6"-(1 ,3,5-triazine-2,4,6- triyltriimino)trihexanoic acid. Among these the aliphatic individuals are especially preferred. Preferred are adipic acid and sebacic acid (decanedioic acid). The abovementioned carboxylic acids are usually present entirely or predominantly as alkali metal, ammonium or substituted ammonium salts even when they are to have been added as free acids. Components used as free carboxylic acids are usually converted by means of sodium or potassium hydroxide, ammonia or appropriate amines into the desired salts, preferably by means of sodium or potassium hydroxide.

[0084] In one embodiment at least one aliphatic monocarboxylic acid is present in the coolants.

[0085] In another embodiment at least one aliphatic dicarboxylic acid is present in the coolants.

[0086] In a preferred embodiment a mixture of at least one aliphatic mono- and at least one aliphatic dicarboxylic acid is present in the coolants.

[0087] As coolant additives the coolant may also comprise in customary small amounts, defoamers (generally in amounts of from 0.003 to 0.008% by weight) and, for reasons of hygiene and safety in the event that it is swallowed, bitter substances (for example of the denatonium benzoate type) and dyes.

[0088] The present invention also relates to a method for improving the anti-corrosion properties of the automotive fluid selected from the lubricant or the coolant in the propulsion system of the electric or hybrid vehicle comprising the step of adding the tetrahydrobenzotriazole of the formula (I) to the lubricant or the coolant. The tetrahydrobenzotriazole is prerably added in an amount of 0.001 to 1.0 wt%, preferably 0.01 to 0.2 wt%. Examples

[0089] Example 1

[0090] A lubricant formulation was prepared by blending the base oil and the additives as shown in Table 1.

[0091] All formulations comprised 10.9 wt% of a commercial viscosity index improver based on a polymethylmethacrylate, 0.5 wt% of Irgalube® 353 (an antiwear additive, liquid ashless dithiophosphate), 0.5 wt% of a 4:1 blend of Irganox® L06 (an alkylated phenyl alpha naphthylamine antioxidant) I Irganox ® L135 (a liquid high molecular weight phenolic antioxidant), 0.05 wt% of Irgacor® L 12 (a liquid alkenyl succinic acid half ester), and were filled up to 100 wt% with a API Group III mineral base oil (3 cSt viscosity at 100 °C).

[0092] For comparison, either no triazole additive (Comparative Example A) or the tolyltriazole of the formula (II) (Comparative Example B) was used.

[0093] Table 1 : Lubricant Formulations Example 2

[0094] The anticorrosion properties were tested by immersing a copper wire (about 60 pm diameter) in the lubricant formulations of Example 1 at 150 °C under a small current. The hours until breaking of the wire was recorded.

[0095] - Comparative Example A broke after 125 hours.

[0096] - Comparative Example B broke after 13.5 hours.

[0097] - Inventive Example 1 did not break within 1000 hours.

[0098] This test demonstrated the excellent anticorrosion properties of the tetrahydrobenzotri azole of the formula (I).

[0099] Example 3

[0100] The anticorrosion properties were tested by immersing a circuit board with enameled copper wires in the lubricant formulations of Example 1 at 150 °C under a small current. After 1000 hours the circuit board was examined for conducting deposits, which were build up over time and lead to an decrease of electrical resistance:

[0101] - Comparative Example A and B showed conducting deposits.

[0102] - Inventive Example 1 did not show any conducting deposits.

[0103] This test demonstrated the excellent anticorrosion properties of the tetrahydrobenzotri azole of the formula (I).

[0104] Example 4

[0105] The corrosion current indicates the tendency of the test specimen to undergo corrosion. The corrosion current can be directly correlated to the corrosion rate, meaning that higher currents reflect higher corrosion rates. In the presence of passivating corrosion inhibitors, the corrosion will be suppressed leading to reduced corrosion currents. The impact of the tetrahydrobenzotriazole on the corrosion currents was determined in a reference engine coolant fluid consisting of:

[0106] 51.0 Water

[0107] 45.9 Monoethylene glycol (MEG)

[0108] 1 .7 2-Ethylhexanoic acid

[0109] 0.2 Sodium hydroxide, 50%

[0110] 1.1 Potassium hydroxide, 48%

[0111] 0.07 Magnesium acetate tetrahydrate, 50%

[0112] 0.02 Denatonium benzoate, 25% in MEG

[0113] 0.006Antifoam

[0114] The test was performed as follows:

[0115] In a potentiostat with a copper working electrode (diameter 10 mm, area 0.79 cm2) and a Ag / AgCI reference electrode 30 g of a 1 :1 mixture of the engine coolant and a corrosive water (148 mg Na2SO4, 165 mg NaCI, 138 mg NaHCOs in 1.0 I water) were heated to 50 °C and the corrosion current was analyzed (average of 3 repetitions) without or with 10 ppm of the tetrahydrobenzotriazole of the formula (I).

[0116] The corrosion current with 10 ppm tetrahydrobenzotriazole of the formula (I) was 21 nA and with 500 ppm it was 20 nA. For comparison the corrosion current without the tetrahydrobenzotriazole of the formula (I) was 444 nA.

[0117] This shows that the tetrahydrobenzotriazole effectively passivates the copper metal surface and inhibits copper corrosion.

Claims

Claims1. A use of a tetrahydrobenzotriazole of the formula (I)for improving an anti-corrosion property of an automotive fluid selected from a lubricant or a coolant in a propulsion system of an electric vehicle.

2. The use according to claim 1 where the automotive fluid comprises 0.001 to 1.0 wt%, preferably 0.01 to 0.2 wt% of the tetrahydrobenzotriazole.

3. The use according to claim 1 or 2 where the automotive fluid is a lubricant.

4. The use according to any of claims 1 to 3 where the anti-corrosion property towards a nonferrous metal is improved.

5. The use according to claim 4 where the nonferrous metal is copper or a copper-containing alloy.

6. The use according to any of claims 1 to 5 where the lubricant comprises a base oil selected from Group III mineral oil, polyalphaolefins, or esters.

7. The use according to any of claims 1 to 6 where the electric vehicle 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.

8. The use according to any of claims 1 to 7 where the coolant comprises from 10 to 90% by weight of alkylene glycols or derivatives thereof, from 90 to 10% by weight of water, and optionally coolant additives.

9. A method for improving an anti-corrosion properties of an automotive fluid selected from a lubricant or a coolant in a propulsion system of an electric or hybrid vehicle comprising the step of adding a tetrahydrobenzotriazole of the formula (I)to the lubricant or the coolant.

10. The method according to claim 9 where the tetrahydrobenzotri azole is added in an amount of 0.001 to 1.0 wt%, preferably 0.01 to 0.2 wt%.

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