Liquid composition for an electrical drive

Abstract

The invention relates to a liquid composition having a dynamic viscosity of 1.5 to 4.0 mm2 / s at 100 DEG C, comprising 50 to 99.93 wt% of a base oil or a mixture of base oils selected from the group consisting of polyalphaolefin oils according to Group IV of API Classification or GTL base oils according to Group III of API Classification; and the following additives:-a boron-containing and ashless succinimide and / or succinimide,-an alkyl-thiadiazole compound according to formula (Ia) and / or (Ib) wherein C9H19 is a tertiary nonyl group. # imgabs0 #

Description

[0001] The present invention relates to a liquid composition which is particularly suitable as a lubricating fluid in a transmission in a drive system of an electric vehicle, in particular an exclusively electric vehicle. The liquid composition according to the invention can also be at least temporarily in contact with power electronics and battery cells and used to cool the power electronics.

[0002] It is known from automotive technology to lubricate the power-transmitting gears in a transmission, whether spur or helical, in order to avoid wear, dissipate the heat generated in the meshing and reduce the friction occurring in the meshing, thereby ensuring their durability and functionality.

[0003] The lubrication is achieved by immersion lubrication or forced lubrication. In immersion lubrication, due to the rotation of the gear during operation, the gear teeth and tooth flanks are immersed in the oil groove and thus absorb the amount of lubricant required for lubrication. In contrast, in forced lubrication, the lubricant is introduced into the meshing of the gears by active lubrication measures.

[0004] The lubricant compositions used for this purpose must have such physicochemical properties that the transmission gears to be lubricated (hereinafter referred to as gearing) can reliably and durably perform their power transmission function. For this purpose, lubricating oils or transmission oils corresponding to the above-mentioned application cases are formulated by adding a plurality of active ingredients (so-called additives) to a rheologically suitable base liquid (so-called base oil), which achieve a property improvement of the base oil system. These additives can be assigned to different chemical classes and act partly by physical action, partly by chemical action or by a combination of both modes of action.

[0005] Engine oils and transmission oils are described by SAE grades (SAE = Society of Automotive Engineers), which specify viscosity measurement temperatures, viscosity limits and grade assignments. In the hot state, the viscosity of all SAE grades of engine and transmission oils is determined uniformly at 100° C. The compositions according to the invention have such favorable viscosity and shear stability properties that a corresponding assignment to the previously applicable SAE classification J 306 is not possible.

[0006] The base oils include, in particular, mineral oils, semi-synthetic and synthetic oils and also natural oils.

[0007] Mineral oils are obtained from petroleum or crude oil usually by distillation or refining and optionally other purification and refining processes. In general, paraffinic components, cycloparaffinic components and aromatic components in crude oil or mineral oil are distinguished, wherein the term paraffinic components represents saturated, unbranched or branched alkanes, and cycloparaffinic components represent cycloalkanes. In addition, according to its source and refining conditions, mineral oils have different proportions of normal alkanes, isoalkanes with low branching degree (so-called monomethyl branched paraffins) and compounds with heteroatoms (particularly O, N and / or S), which are said to have slight polar properties.

[0008] Synthetic base oils include, in particular, organic esters, such as diesters and polyol esters, polyalkylene glycols, polyethers, synthetic hydrocarbons such as polyols, α Olefins (PAO), silicone oils and perfluoroalkyl ethers.

[0009] Natural oils are animal or vegetable oils, such as hoof oil or jojoba oil.

[0010] The base oils can also be used as mixtures and are generally commercially available.

[0011] Lubricating fluids usually contain various substances to improve certain properties in a targeted manner. For example, these additives (additives) are used to improve load-bearing capacity and wear protection (high pressure and anti-wear additives), foaming behavior (foam inhibitors), friction properties (friction modifiers) and oxidation and corrosion stability (oxidation inhibitors, metal passivators, rust inhibitors). Dispersants and detergents are also used as additives. In addition, flow improvers, such as so-called viscosity index (VI) improvers (higher molecular weight thickeners) can be added in a dosage of about 5.0 to 1 5.0% by weight and / or pour point depressants in a dosage of about 0.2 to 2.0% by weight.

[0012] Compared to a transmission in combination with a conventional internal combustion engine, the torque of an electric drive is relatively constant across the entire speed range, even when starting to drive. The speed levels of electric drives and their gear units are significantly higher. Electrical and electronic components and elements come into contact with lubricants in part, either through direct wetting with the lubricants or through penetration of lubricants into gaps related to design and production so that the lubricants can reach the electrical and electronic components. It has therefore been found that chemically active sulfur-containing additives contained in the lubricants react with the metals of the electrical and electronic components, especially copper and silver, in sulfur corrosion reactions, which can lead to impaired functionality of the electrical components.

[0013] Wear protection additives that are usually used for transmission oils are compounds containing sulfur and / or phosphorus and / or zinc and / or halogens. In particular, special high-pressure wear-resistant additives (so-called extreme pressure (EP) additives) are used, the basic chemical structure of which is long-chain hydrocarbons bridged to one another by sulfur chains. Examples include polysulfides, sulfided olefins and sulfided esters. These sulfur compounds have a very strong tendency to decompose to form active sulfur when they come into contact with non-ferrous metals (for example copper or silver), which forms sulfides with the above-mentioned metals. It is also known to use triaryl phosphates, zinc dialkyl dithiophosphates, dithiocarbamates and dimercaptothiadiazoles.

[0014] For example, if a thiol comes into contact with a copper surface, a copper-thiol complex is first formed, followed by a redox process in which the thiol is oxidized to a disulfide and Cu(II) is reduced to Cu(I).

[0015] Document US 4,217,232 discloses the reaction product of polysulfide and Grignard reagent as an antioxidant in lubricants. Document US 3,873,454 discloses similar sulfur-rich additives as high-pressure additives for lubricants. Document US 4,194,980 describes a similar high-pressure lubricant having a component formed by reacting a sulfur-containing olefin with a cyclic polydisulfide.

[0016] Document US 2022 / 0041951 A1 describes a lubricant containing a phosphorus-containing dispersant containing 2-3.5 wt. % phosphorus. It may also contain mercaptothiadiazole and boron-treated succinimide. The lubricating fluid viscosity claimed is 3.0 to 6.5 mm 2 / s, which is measured at 100°C.

[0017] Document WO 2017 / 079017 A1 discloses a lubricant for electric transmission chains, which contains a wear protection additive having 0.3-2.0% of an amine salt of a phosphorus compound obtained from P2S5, an alcohol, an alkylene oxide and P2O5. The viscosity measured at 100°C is 3 to 7.5 mm 2 / s. In addition, the lubricant contains 0.5-7% by weight of sulphurised olefins. The salt has in particular the structure (RO)2PS-SH, which reacts with propylene oxide, wherein R in particular can be an alkyl group, such as 2-methyl-4-pentyl. It can also contain dithiothiadiazole and ashless succinimide.

[0018] Document EP 2 960 321 A1 describes lubricating fluids with additives which result in a dynamic viscosity of 2.5-4.0 mm at 100° C. 2 / s.

[0019] Document WO 2020 / 264154 A1 / US 2020 / 039608 describes a process for producing methyl paraffin from linear alpha olefin (LAO) dimers using a metallocene catalyst system. The use as a heat transfer fluid for cooling batteries in electric vehicles is claimed. Favorable heat transfer properties are mentioned.

[0020] The difficulty in developing optimal lubricating fluid compositions is to find those which fully meet the specific requirements for lubrication in electric drives of gears and rolling bearings at high speeds, continuously high torques and simultaneously low friction, and at the same time do not cause corrosive changes in and on the surfaces of electrical and electronic components which come into direct contact with the fluid.

[0021] The object of the present invention is therefore to find an optimized lubricating fluid composition for electric motors or electric drives.Metals such as copper and silver should be damaged as little as possible or not at all by contact.

[0022] The invention is intended to achieve good efficiency in a transmission of an electric drive train.

[0023] The subject of the present invention is a 0.8 to 4.0 mm 2 / s, preferably 2.0 to 2.8 mm 2 / s, particularly preferably 2.2 to 3.1 mm 2 A liquid composition having a low dynamic viscosity (measured at 100° C. according to ASTM D 445) of 1:1 to 1:1, comprising

[0024] 50-99.93% by weight of a base oil or base oil mixture selected from polyalphaolefin oils according to API classification group IV or GTL base oils according to API classification group III;

[0025] And the following additives:

[0026] Borated, ashless succinamides and / or succinimides,

[0027] - Alkyl-thiadiazole compounds according to formula (Ia) and / or (Ib),

[0028]

[0029] Among them, C9H 19 It is tert-nonyl.

[0030] Comprehensive studies using known and purposefully newly developed tribological test methods and measuring methods revealed that these test oil formulations have surprisingly very different results with regard to the efficiency of the transmission tests using the drive concept described. The test results show that it is not possible to predict the efficiency behavior based solely on the viscosity data. In addition, it was also found almost continuously that the lubricant additives have unexpectedly strong synergistic and antagonistic effects on the friction behavior and therefore the efficiency behavior of the test oils in the test methods and the transmission.

[0031] Lubricating fluids based on low-viscosity synthetic oils based on polymers have been found to be advantageous. α Olefin PAO, especially linear α The combination of olefin (LAO) dimers, which have particularly good evaporation loss behavior at high temperatures, and therefore selected ashless and boron-treated succinimide dispersants (PIBSA / PAM) and 2,5-alkyl-thiadiazole compounds. Surprisingly, negative effects could be found when using too high or too low amounts of the claimed thiadiazoles in combination with sulfur-phosphorus compounds (e.g. phosphates) added in order to obtain sufficient wear behavior as required. This indicates that unpredictable and strong interactions occur between the various additives in the above-mentioned base oil system.

[0032] To improve material compatibility, in particular with copper and seals, the advantageous selection of boron-containing dispersant additives based on PIBSI and PIBSA has proven to be advantageous, but surprisingly in significantly lower dosages compared to formulations for use as lubricants for dual clutch transmissions or so-called stepped automatic transmissions.

[0033] The boron-containing and ashless succinamide and / or succinimide used in the liquid composition according to the present invention act as a dispersant with relatively low MW based on PIBSA / PIBSI / PAM, preferably prepared into different molecular weights by maleic anhydride (MAN) and polyisobutylene (PIB) in industry, wherein for PIB, according to the manufacturer, the traditional less reactive and newer more reactive PIB and mixtures thereof are distinguished. The preparation of suitable dispersants based on succinimide is described in, for example, US897696 B2, in paragraphs 41-47. The dispersant preferably used can be optionally treated with phosphorus and is boron-treated. When preparing succinimide, DETA or TETA are preferably used in polyamines, particularly preferably TEPA. Suitable dispersants are also described in EP 0 840775 B1.

[0034] The choice of PIB affects the properties of the product. Dispersant additives are industrial products with resulting properties.

[0035]

[0036] PIBSA (Polyisobutylene succinic anhydride)

[0037] In the combination according to the invention with the claimed additive and the dosage according to the invention, the necessary low viscosity of the liquid composition can be ensured using a selected succinimide dispersant with a MW preferably of 600 to 1050. This produces more favorable results in terms of efficiency and compatibility with polymer materials compared to a higher MW of 2000. In addition, at relatively lower dosages than usual, these dispersants still produce sufficient cleanliness (no precipitation, no unwanted deposits) at high application temperatures without impairing the cold flow properties. Surprisingly, only certain combinations have proven to be advantageous. If the amount of phosphate ester is increased too much, the load-bearing capacity decreases significantly. Through targeted use, good compatibility with uncoated copper wire materials and with special metal wires used in windings of electric motors by means of special protective lacquer layers is particularly ensured.

[0038] In this regard, 2-tert-nonyl-thiadiazole compounds according to formula (Ia) and / or (Ib), i.e. 2-tert-nonyldisulfide-5-mercapto-[1,3,4]-thiadiazole according to formula (Ib) and / or 2,5-bis(tert-nonyldisulfide)-[1,3,4]-thiadiazole according to formula (Ia) are used as so-called extreme pressure (EP) additives, and the proportion is preferably 0.05 to 1.0% by weight, in particular 0.2 to 0.8% by weight. Compared to other alkyl groups, tert-nonyl has proven to be particularly effective.

[0039] The base oil may be at least one selected from the following:

[0040] 80.0-99.5% by weight of a base oil selected from polyalphaolefin oils with C20 or C24 chains according to API classification group IV, such as Chevron Synlube 2.5, having a dynamic viscosity at 100°C of 1.0-4.2, preferably 2.0 to 2.5 mm 2 / s, particularly preferably 2.1 to 2.4 mm 2 / s,

[0041] A base oil mixture containing 15.0-85.0% by weight of a base oil selected from the group consisting of polyols with C20 chains and / or C24 chains according to API classification group IV. α Olefin oils, such as Chevron Synlube 2.5, having a dynamic viscosity of 1.0-4.2 mm2 measured at 100°C 2 / s, preferably 2.0-2.5mm 2 / s, particularly preferably 2.0-2.6mm 2 / s, additionally containing 1-50% GTL 3 (chain length C18-C50 branched and unbranched, C123H2520) produced according to the Fischer-Tropsch process, according to the structure (see EC / list number: 482-220-0, CAS number: 848301-69-9)

[0042] 50.0-99.95% by weight of base oil selected from special polymers according to API classification group IV produced by metal catalysts with excellent low evaporation loss behavior at high temperatures α Olefin oil, whose dynamic viscosity at 100°C is 0.9-4.2, preferably 1.2 to 2.6 mm 2 / s, particularly preferably 2.0-2.4 mm 2 / s,

[0043] 50.0-99.95% by weight of a base oil selected from special polyalphaolefin oils according to API classification group IV produced by metal catalysts with excellent low evaporation loss behavior at high temperatures, and having a dynamic viscosity at 100°C of 0.9-4.2, preferably 0.9-1.5 mm 2 / s, particularly preferably 1.2-1.4 mm 2 / s,

[0044] 10.0-88.00 wt. % of a base oil selected from special linear polyolefins according to API classification group IV produced by metal catalysts with excellent low evaporation loss behavior at high temperatures and having a dynamic viscosity at 100° C. of 0.9-4.2, preferably 2.0-4.0 mm 2 / s, particularly preferably 3.2-3.5mm 2 / s.

[0045] The additives may in particular be the following:

[0046] At least one of the three boron-containing succinimide dispersants, with a total concentration of 0.2-4.0% by weight,

[0047] 0.1-3% of a boron-containing, ashless dispersant based on polyisobutylene succinimide (PI BSA or PI BSI) having a molecular weight MW of 500-1300, preferably 900-1100 molecular weight, particularly preferably 950-1050, made from maleamide and / or maleimide,

[0048] - Alkyl-thiadiazole compounds according to formula (Ia) and / or (Ib), in particular 1,3,4-thiadiazolidine-2,5-dithione, which are preferably obtained as reaction products of hydrogen peroxide and tert-nonanethiol.

[0049] The dynamic viscosity is determined according to the ASTM D445 test method. At -40°C, the viscosity is below 2000 mPas (measured according to DIN 51 398), preferably even <1500 mPas. The API classification of the oil is the classification of the American Petroleum Institute (API).

[0050] Unless otherwise stated, the data concerning the content or concentration of the individual components made within the scope of the present invention are based on the entire lubricating fluid composition.

[0051] The present invention also relates to the use of the lubricating fluid composition according to the invention in electronic components, such as battery-driven vehicles, electric drives and high-speed transmissions in combination with electric motors. Copper and silver are often used in these electronic components.

[0052] It is also contemplated that the lubricant composition may contain other additives tailored to the base oil, such as wear protection additives, antioxidants, metal deactivators, rust inhibitors, dispersants, friction modifiers and foam inhibitors.

[0053] The composition according to the invention advantageously allows the use of relatively low concentrations of conventional flow improvers of only <0.5 wt. %, since in the prior art, so-called flow improvers (viscosity index (VI) improvers and pour point depressants), such as higher molecular weight thickeners, are usually added in amounts of 5 to 15 wt. % in order to modify the flow properties of the base oil.

[0054] Advantageously, the invention makes it possible to use no or only small amounts of polysulfides and still achieve good lubrication properties. This prevents or slows down the chemical attack on copper that occurs in electric motors, batteries and the like.

[0055] The liquid composition according to the invention is characterized by excellent thermal conductivity properties when used as a coolant and in a transmission.

[0056] Furthermore, no or only little corrosion is observed on electrical or electronic components and varnished copper wires used in the windings of electric motors or drive machines. At the same time, the lubricant composition ensures very good lubrication of the gear arrangement and very low drag losses due to very low friction values ​​in the tribological contact.

[0057] Advantageously, the liquid composition according to the invention also has good compatibility with elastomeric materials and polyamides used in transmissions and drive chains, such as special radial shaft seals (RWDR) made of ACM, even at relatively high rotational speeds or high application temperatures. There is also good compatibility with uncoated copper wire materials.

[0058] Furthermore, there is sufficient chemical compatibility with relatively sensitive sealants, for example silicone-containing liquid sealants, which can be achieved in particular by the targeted use of the claimed boron-treated succinimide in combination with a P / S compound.

[0059] In addition to 1.5 to 3.1 mm at 100 ° C 2 In addition to a low viscosity of less than 2000 mPas at -40°C (measured using the test method ASTM D445) or less than 2000 mPas at -40°C (measured in accordance with DIN 51398), the composition according to the invention advantageously has a shear loss (viscosity after shearing) of less than 5% in accordance with ASTM D445. This advantageously makes it impossible to classify it in the internationally applicable SAE classification J 306 for transmission oils (as of 2019), since only significantly higher viscosity levels (>3.8 mm at 100°C) have been defined there so far. 2 / s).

[0060] In a preferred embodiment of the present invention, the liquid composition additionally comprises a phosphorus compound or a phosphorus-sulfur compound according to formula (II):

[0061]

[0062] Particularly preferred in this embodiment are ammonium salts of phosphorus compounds according to formula (II) wherein at least one group on the ammonium cation is a C 1 2 -C 1 4 tertiary alkyl group.

[0063] In one embodiment, the liquid composition comprises the reaction product of 4-methyl-2-pentanol and phosphorus pentasulfide, which is propoxylated and esterified with phosphorus pentoxide and salified with an amine and has a C 1 2-14-tertiary alkyl group.

[0064] Furthermore, the liquid composition may contain up to 6% by weight, in particular 3 to 6% by weight, of dispersed polymethacrylates. Polymethacrylates are esters of polymethacrylic acid which are esterified, for example, with alkyl alcohols such as C1-C4-alkyl, in particular with methanol (resulting in polymethyl methacrylate, PMMA).

[0065] In a likewise preferred embodiment of the invention, the base oil further comprises a GTL base oil according to API classification group III. The suitability for use in electronic components is advantageously improved. The classification of the base oils is given in table form in the examples.

[0066] The composition according to the invention preferably comprises a flow improver (PPD) in an amount of <0.5% by weight, wherein the flow improver is selected from the group consisting of hydrogenated polystyrene-isoprene copolymers (HSI), ethylene-propylene copolymers (OCP), polyisobutylene (PIB), polyalkyl acrylates and polyalkyl methacrylates and copolymers thereof (PAMA), vinylpyrrolidone / methacrylate copolymers, polyvinylpyrrolidone, polybutene, olefin copolymers, styrene / acrylate copolymers, polyethers, alkylated naphthalene derivatives and mixtures thereof. Particular preference is given to polyalkyl acrylates and polyalkyl methacrylates.

[0067] In a preferred embodiment of the present invention, the boron content of the composition is 20 to 300 mg / kg.

[0068] The composition preferably contains no or only small amounts of 0 to <0.4% of sulfur compounds of the sulfurized olefin type, which have an unfavorable corrosion behavior toward copper materials.

[0069] The sulfur content in the lubricating fluid composition according to the invention is preferably from 0.05 to 0.25% by weight, particularly preferably from 0.07 to 0.13% by weight.

[0070] In the present case, the sulfur content relates to the total content of bound and unbound sulfur in the composition, which is contained in the sulfur compounds of the alkyl-thiadiazole compounds according to formula (I) and, in a preferred embodiment, in the ammonium salts of the phosphorus compounds according to formula (II). The sulfur that may be present in the base oil and the conditioning oil from additives is considered to be 0.01 to 0.05% by weight (PAO / GtL only residual sulfur). The sulfur content describes an analytical standard parameter in the quality assurance of transmission oils.

[0071] In a preferred embodiment of the invention, the phosphorus content of the composition is from 0.02 to 0.1% by weight, in particular in the form of phosphorus present in combination in various additives. In this case, the phosphorus content is based on the total content of bound and unbound phosphorus in the composition, which includes phosphorus that may be present in the base oil and phosphorus present in combination in the corresponding additives. Phosphorus-containing additives are known to improve the lubricity of the composition against abrasive wear.

[0072] In a preferred embodiment of the composition according to the invention, the dynamic viscosity measured at 100° C. is between 1.5 and 3.3 mm 2 / s (centistokes), preferably 2.0 to 2.9 mm 2 / s, particularly preferably 2.5 to 2.9 mm 2 / s. The viscosity within the above range is particularly suitable for lubricating the transmission in the electric drive.

[0073] To modify the flow properties of the base oils, 5 to 15% by weight of so-called flow improvers (viscosity index (VI) improvers and pour point depressants), such as higher molecular weight thickeners, are usually added. The compositions according to the invention preferably contain these conventional flow improvers only in relatively low concentrations of <0.5% by weight.

[0074] For target viscosities of the finished formulated lubricant of KV1 00 = 3 cSt or lower, GTL 3 and optionally GTL 4 are particularly preferred (see Table 1).

[0075] Table 1:

[0076]

[0077] Table 2: Typical data of GTL according to the technical data sheet compared to PAO

[0078]

[0079] Synthetic base oils of Group III and Group IV as specified in the American Petroleum Institute (API) "Base Oil Interchangeability Guide" can be used as base oils for the lubricant composition according to the present invention. Groups I to V of the API base oil groups are listed in Table 3.

[0080] Table 3:

[0081]

[0082] 1 Groups I to III are mineral oil based materials.

[0083] 2 ASTM D1552, ASTM D2622, ASTM D3120, ASTM D4294 or ASTM D4927.

[0084] 3 ASTM D2007

[0085] 4 ASTM D2270

[0086] Further preferred embodiments of the invention result from the remaining features mentioned in the dependent claims.

[0087] Unless stated otherwise in individual cases, the individual embodiments of the invention mentioned in this application can advantageously be combined with one another. Example

[0088] Material

[0089] Base oil: Syn 2.5: Chevron Synfluid 2.5

[0090] PAO4: Polyalphaolefin 4

[0091] HC 3 / 4

[0092] Viscosity improver: D-PMA: Dispersed polyalkyl methacrylate

[0093] Dispersant: B-PP: Boron-treated PIBSA / PAM succinimide

[0094] PP: Boron-free PIBSA / PAM succinimide

[0095] Extreme pressure additives: EP 1: AT: with C9H 19 (tert-nonyl)alkyl-thiadiazole;

[0096] According to (Ia) / (Ib)

[0097] EP 2: Olefinic polysulfides

[0098] Wear protection additive: AW 1: phosphoric acid compound (reaction product of 4-methyl-2-pentanol and phosphorus pentasulfide, which is propoxylated, esterified with phosphorus pentoxide and salified with an amine and has a C12-14 tertiary alkyl group; according to (II)

[0099] AW 2: Alkyl amine phosphate

[0100] AW 3: 353(BASF)

[0101] AW4: Alkyl phosphite

[0102] AW5: Dibutyl phosphonate

[0103] AW6: Amine-neutralized phosphate ester

[0104] Friction value improver: FM 1: molybdenum dicarbamate

[0105] FM 2: Ethoxylated amines

[0106] Anti-corrosion additive: KS 1: Triazolidine alkyl amine

[0107] KS 2: TTZ(BASF)

[0108] KS 3: Alkylbenzotriazolidine amine

[0109] Antioxidant: AO 1: Bisnonylaniline

[0110] AO 2: Diphenylamine

[0111] Conditioning oil

[0112] Examples 1 to 10

[0113] The compositions according to Table 4 were prepared by mixing, wherein all data refer to % by weight.

[0114] Various physical and thermodynamic properties of the compositions of Examples 1 to 10 were investigated. The results are summarized in Tables 5 to 8.

[0115] The elemental compositions of the compositions of Examples 1 to 10 are shown in Table 9, where all data refer to mg / kg of total composition. Example 10 is a typical modern manual transmission oil, which has excellent lubricating properties, but the thermal stability and compatibility with copper are not sufficient for use in the electric drive train of electric motors. The efficiency also appears to be significantly less favorable.

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

Claims

1. Dynamic viscosity at 100°C is 0.8 to 4.0 mm 2 / s of liquid composition, comprising 50-99.93% by weight of a base oil or base oil mixture selected from polyalphaolefin oils according to API classification group IV or GTL base oils according to API classification group III; And the following additives: Borated, ashless succinamides and / or succinimides, - Alkyl-thiadiazole compounds according to formula (Ia) and / or (Ib), Among them, C9H 19 It is tert-nonyl.

2. The liquid composition according to claim 1, further comprising at least one of the following phosphorus compounds (II): Preference is given to the reaction product of 4-methyl-2-pentanol and phosphorus pentasulfide which is propoxylated, esterified with phosphorus pentoxide and salified with an amine and has a C12-14 tertiary alkyl group.

3. A liquid composition according to any one of claims 1 or 2, wherein the boron-containing and ashless succinamide and / or succinimide is a dispersant based on polyisobutylene succinamide or polyisobutylene succinimide (PIBSA or PIBSI) made from maleamide or maleimide.

4. The liquid composition according to any one of claims 1 to 3, wherein the proportion of the boron-containing and ashless succinamide and / or imide is 0.2 to 4.0% by weight.

5. The liquid composition according to any one of claims 1 to 4, wherein the molecular weight MW of the boron-containing and ashless succinamide and / or succinimide is 500 to 1300, preferably 900 to 1100, particularly preferably 950 to 1050.

6. The liquid composition according to any one of claims 1 to 5, wherein the proportion of the alkyl-thiadiazole compound according to formula (Ia) and / or (Ib) is from 0.05 to 1.0% by weight.

7. The liquid composition according to any one of claims 1 to 6, further comprising the thiophosphite EG424-820-7.

8. The liquid composition according to any one of claims 1 to 7, further comprising a flow improver in an amount of <0.5 wt%, wherein the flow improver is selected from hydrogenated polystyrene-isoprene copolymers (HSI), ethylene-propylene copolymers (OCP), polyisobutylene (PIB), polyalkyl acrylates and polyalkyl methacrylates and copolymers thereof (PAMA), vinyl pyrrolidone / methacrylate copolymers, polyvinyl pyrrolidone, polybutene, olefin copolymers, styrene / acrylate copolymers, polyethers, alkylated naphthalene derivatives and mixtures thereof.

9. The liquid composition according to any one of claims 1 to 8, wherein the boron content thereof is 20 to 300 mg / kg.

10. The liquid composition according to any one of claims 1 to 9, wherein the sulfur content is from 0.05 to 0.25% by weight, in particular from 0.07 to 0.13% by weight.

11. The liquid composition according to any one of claims 1 to 10, wherein the phosphorus content is 0.02 to 0.1 wt%.

12. The liquid composition according to any one of claims 1 to 11, wherein the dynamic viscosity at 100°C is 2.0 to 2.8 mm 2 / s, especially 2.2 to 3.1 mm 2 / s.

13. Use of the liquid composition according to any one of claims 1 to 12 in battery-driven vehicles, electric drives and high-speed transmissions in combination with electric machines.

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