Liquid composition for use in electric drives

Abstract

The invention relates to a liquid composition having a dynamic viscosity in the range of 1.5 – 4.0 mm2 / s at 100°C, comprising: - 50-99.93 wt.% of a base oil or base oil blend, selected from polyalphaolefin oils of group IV of the API classification or GTL base oils of group III of the API classification; and the following additives: - a boron-containing, ashless succinic acid amide and / or succinic acid imide, - an alkyl thiadiazole compound according to formula (Ia) and / or (Ib), wherein C9H19 is tert-nonyl.

Description

[0001] The invention relates to a fluid composition that is particularly suitable as a lubricant in transmissions in a drive system of electrically powered vehicles, especially exclusively electrically powered vehicles. The fluid composition according to the invention can additionally come into contact, at least temporarily, with power electronics and a battery cell and serve to cool the power electronics.

[0002] In automotive engineering, it is known that power-transmitting gears in transmissions, whether straight or helical, are lubricated to prevent wear, to dissipate heat generated in the tooth mesh and to reduce friction in the tooth mesh, in order to ensure their durability and functionality.

[0003] Lubrication is achieved through immersion or forced lubrication. In immersion lubrication, the teeth and tooth flanks of the gears are immersed in an oil sump due to the rotation of the gears during operation, thereby absorbing the necessary amount of lubricant. In contrast, with forced lubrication, the lubricant is actively introduced into the meshing of the gear teeth through oiling mechanisms.

[0004] The lubricant composition used for this purpose must have such physicochemical properties that the gears to be lubricated (hereinafter referred to as gear teeth) can reliably and durably perform their power-transmitting function. For this purpose, lubricating or gear oils corresponding to the application described above are formulated by combining rheologically suitable base fluids (the so-called base oils) with numerous active ingredients (the so-called additives) that improve the properties of the base oil system. These additives belong to various chemical classes and act partly physically, partly chemically, or through a combination of both modes of action.

[0005] Engine and transmission oils are described using SAE grades (SAE = Society of Automotive Engineers), which define temperatures for viscosity measurements, viscosity limits, and class assignments. In the hot state, the viscosity of engine and transmission oils is determined uniformly for all SAE grades at 100 °C. The composition according to the invention exhibits such favorable viscosity and shear stability properties that a corresponding classification in the previously valid SAE classification J 306 is not possible.

[0006] Base oils include, in particular, mineral oils, semi-synthetic and synthetic oils, and natural oils.

[0007] Mineral oils are generally obtained from petroleum or crude oil through distillation or refining, and optionally further purification and refining processes. Generally, a distinction is made between paraffinic, naphthenic, and aromatic components in crude oils or mineral oils, with the terms paraffinic component referring to saturated, unbranched, or branched alkanes and naphthenic component to cycloalkanes. Furthermore, depending on their origin and refining, mineral oils contain varying proportions of n-alkanes, iso-alkanes with a low degree of branching (so-called monomethyl-branched paraffins), and compounds with heteroatoms, particularly O, N, and / or S, which are attributed with slightly polar properties.

[0008] Synthetic base oils include, among others, organic esters such as diesters and polyol esters, polyalkylene glycols, polyethers, synthetic hydrocarbons such as polyalphaolefins (PAO), silicone oils and perfluoroalkyl ethers.

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

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

[0011] Lubricating fluids typically contain various substances to specifically improve certain properties. These additives serve, for example, to improve load-carrying 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. Additionally, flow improvers, so-called viscosity index (VI) improvers (higher molecular weight thickeners), can be added in dosages of approximately 5.0 to 15.0 wt.%, and / or pour point depressants in dosages of approximately 0.2 to 2.0 wt.%.

[0012] Compared to manual transmissions in conjunction with conventional combustion engines, electric drives maintain a relatively constant torque across the entire speed range, even during start-up. The rotational speed of electric drives and their gears is significantly higher. The electrical and electronic components are partially in contact with the lubricating oil, either through direct contact or through the oil penetrating design and manufacturing gaps, allowing it to reach the electrical and electronic components. Consequently, additives containing chemically active sulfur in the lubricating oil can react with the metals (especially copper and silver) of the electrical and electronic components, producing sulfur-corrosive reactions that can impair their function.

[0013] The anti-wear additives typically used in gear oils are compounds containing sulfur and / or phosphorus and / or zinc and / or halogens. In particular, special high-pressure wear additives (so-called extreme-pressure (EP) additives) are used, which in their basic chemical structure consist of long-chain hydrocarbons linked by a sulfur chain. Examples include polysulfides, sulfurized olefins, and sulfurized esters. These sulfur compounds have a strong tendency to decompose upon contact with non-ferrous metals (for example, copper or silver), forming active sulfur compounds that react with these metals to form sulfides. Triaryl phosphates, zinc dialkyldithiophosphates, dithiocarbamates, and dimercaptothiadiazoles are also commonly used.

[0014] For example, when thiols come into contact with copper surfaces, copper thiolate complexes are initially formed, accompanied by a redox process in which thiols are oxidized to disulfides and Cu(II) is reduced to Cu(I).

[0015] Document US 4,217,232 discloses reaction products of polysulfides with a Grignard reagent as antioxidants in lubricants. Document US 3,873,454 discloses a similar sulfur-rich additive as a high-pressure lubricant additive. Document US 4,194,980 describes yet another similar high-pressure lubricant with ingredients formed by the reaction of sulfur-containing olefins with cyclic polydisulfides.

[0016] Document US 2022 / 0041951 A1 describes a lubricant containing a phosphorus-based dispersant with a phosphorus content of 2-3.5 wt%. It may also contain mercaptothiadiazoles and borated succinimides. The claimed viscosity of the lubricant is 3.0 to 6.5 mm² / s, measured at 100°C.

[0017] Document WO 2017 / 079017 A1 discloses a lubricant for use in electric powertrains containing an anti-wear additive with 0.3–2.0% of an amine salt of a phosphorus compound, obtained from P₂S₅, an alcohol, alkylene oxide, and P₂O₅. The viscosity is 3 to 7.5 mm² / s, measured at 100°C. The lubricant also contains sulfurized olefins of 0.5–7 wt%. The salt has, among other structures, (RO)₂PS-SH, which is reacted with propylene oxide, where R can be, among other things, an alkyl group such as 2-methyl-4-pentyl. It may also contain dimercaptothiadiazole and an ashless succinimide.

[0018] Document EP 2 960 321 A1 describes a lubricating fluid with additives that results in a kinematic viscosity at 100°C of 2.5 - 4.0 mm² / s.

[0019] Document WO 2020 / 264154 A1 / US 2020 / 039608 describes the production process of methyl paraffins from dimers of linear alpha-olefins (LAOs) using a metallocene catalyst system. It claims an application as a heat transfer fluid for cooling a battery in an electric vehicle. Advantageous heat transfer properties are mentioned.

[0020] Other lubricant compositions are known from US 2020 / 332 218 A1, US 2010 / 0 130 390 A1, EP 3 786 264 A1 and WO 2021 / 193 869 A1 (EP 4 130 208 A1).

[0021] The difficulty in developing an optimal lubricant composition lies in finding one that fully meets the specific lubrication requirements in electric drives for gears and rolling bearings at high speeds and consistently high torques with low friction, while simultaneously not causing any corrosive changes in and on electrical and electronic components that are in direct contact with the fluid.

[0022] The invention is therefore based on the objective of finding an optimized lubricant composition suitable for use in electric motors or electric drives. Metals such as copper and silver should be affected as little as possible, or not at all, by contact.

[0023] The invention is intended to allow for a favorable efficiency in a gearbox of an electric drive train.

[0024] The invention relates to a liquid composition according to claim 1 having a low kinematic viscosity (measured according to ASTM D 445 at 100°C) in the range of 0.8 to 4.0 mm² / s, preferably 2.0 to 2.8 mm² / s, particularly preferably 2.2 to 3.1 mm² / s, comprising 50-99.93 wt.% of a base oil or base oil mixture selected from polyalphaolefin oils according to Group IV of the API classification or GTL base oils according to Group III of the API classification; and the following additives: 0.2 to 4.0 wt.% of a boron-containing, ash-free succinic amide and / or imide, 0.05 to 1.0 wt.% of an alkyl thiadiazole compound according to formula (1a) and / or (1b), where C 9 H 19 is tert-nonyl, and phosphorus compounds (II) as described later.

[0025] Comprehensive investigations using both established and newly developed tribological testing procedures and measurement methods revealed surprisingly diverse results for these experimental oil formulations regarding efficiency in gearbox tests with the described drive concepts. The test results demonstrated that predicting efficiency behavior based solely on viscosity data is not possible. Furthermore, an unexpectedly strong, both synergistic and antagonistic, influence of lubricant additives on the friction and thus the efficiency behavior of the experimental oils was observed almost consistently in the test procedures and gearboxes.

[0026] Lubricating fluids based on low-viscosity synthetic oils derived from poly-α-olefins (PAOs) proved advantageous, particularly combinations of linear alpha-olefin (LAO) dimers exhibiting exceptionally good evaporation loss behavior at high temperatures. Combinations with selected ashless boronized succinimide dispersants (PIBSA / PAM) and 2,5-alkyl thiadiazole compounds were also found to be effective. Surprisingly, a negative impact was observed when using excessively high or low amounts of the thiadiazoles in combination with the sulfur-phosphorus compounds (such as phosphoric acid esters) added to maintain adequate wear resistance. This revealed unexpectedly strong interactions between the various additives in the aforementioned base oil systems.

[0027] To improve material compatibility, especially with copper and seals, an advantageous selection of boron-containing dispersant additives based on PIBSI and PIBSA has proven effective, although surprisingly in significantly lower dosages than in formulations for applications as lubricating oils for dual-clutch transmissions or so-called ATF oils for automatic transmissions.

[0028] The boron-containing, ash-free succinic amides and / or imides used in the liquid composition according to the invention act as dispersants with a comparatively low molecular weight. Based on PIBSA / PIBSI / PAM, they are preferably produced industrially from maleic anhydrite (MAN) with polyisobutylene (PIB) in different molecular weights. Depending on the manufacturer, a distinction is made between conventional, less reactive PIBs and newer, more reactive PIBs and mixtures thereof. The production of suitable dispersants based on succinimides is described, for example, in US 897696 B2, paragraphs 41-47. The preferably used dispersants can optionally be phosphorus-treated and are boronized. For the production of the succinimides, DETA or TETA polyamines are preferably used, and TEPA is particularly preferred. Suitable dispersants are also described in EP 0 840 775 B1.

[0029] The choice of PIB (Product Ingredient Biological Agent) affects the properties of the products. Dispersant additives are technical products with resulting properties. PIBSA (polyisobutene succinic anhydride)

[0030] In the combination according to the invention with the claimed additives and the dosage according to the invention, the necessary low viscosity of the liquid composition can be ensured with the selected succinimide dispersants with a molecular weight (MW) preferably of 600 to 1050. This results in more favorable outcomes with regard to efficiency and compatibility with polymer materials compared to higher MW values ​​of 2000. Furthermore, these dispersants, even at a comparatively lower dosage than usual, still lead to sufficient cleanliness (no sludge formation, no undesirable deposits) at high application temperatures without impairing the low-temperature flow properties. Surprisingly, only certain combinations proved advantageous. If the amount of phosphoric acid ester is increased too much, the corrosion resistance decreases significantly.In particular, targeted application ensures good compatibility with both uncoated copper wire materials and special wires that are used with special protective lacquer coatings for use in windings of electric machines.

[0031] The composition contains the 2- tert -Nonyl-thiadiazole compound according to formula (1a) and / or (1b), i.e. 2- tert -Nonyldithio-5-mercapto-[1,3,4]-thiadiazole according to formula (Ib) and / or 2,5-bis( tert- Nonyldithio)-[1,3,4]-thiadiazole according to formula (aa) is used as a so-called extreme pressure (EP) additive and has a proportion of 0.05 to 1.0 wt%, in particular 0.2 to 0.8 wt%. The tert-nonyl group has proven to be particularly effective compared to other alkyl groups.

[0032] The base oil can be, in particular, at least one of the following selected from: 80.0–99.5 wt.% of a base oil selected from polyalphaolefin oils with C20 or C24 chain, such as Chevron Synlube 2.5, with a dynamic viscosity in the range of 1.0–4.2, preferably 2.0–2.5 mm² / s at 100°C, particularly preferably 2.1–2.4 mm² / s according to Group IV of the API classification. A base oil mixture containing 15.0–85.0 wt.% of a base oil selected from polyalphaolefin oils with C20 and / or C24 chain, such as Chevron Synlube 2.5, with a kinematic viscosity in the range of 1.0–4.2 mm² / s, measured at 100°C, preferably 2.0–2.5 mm² / s, particularly preferably 2.0–2.6 mm² / s according to Group IV of the API classification. API classification and additionally containing synthetic oils 1-50% GTL 3 produced according to the Fischer-Tropsch process (chain length C18-C50 branched and unbranched, C123H2520) according to the structure (see EC / List no.: 482-220-0, CAS no.: 848301-69-9) 50.0 -99.95 wt.-% of a base oil selected from special polyalphaolefin oils with excellent low evaporation loss behavior at high temperatures, produced using metal catalysts with a kinematic viscosity in the range of 0.9 - 4.2, preferably 1.2 to 2.6 mm² / s at 100°C, particularly preferably 2.0 to 2.4 mm² / s according to Group IV of the API classification. 50.0 - 99.95 wt.% of a base oil selected from special polyalphaolefin oils with excellent low evaporation loss behavior at high temperatures, produced using metal catalysts with a kinematic viscosity in the range of 0.9 - 4.2, preferably 0.9 to 1.5 mm² / s at 100°C, particularly preferably 1.2 to 1.4 mm² / s according to Group IV of the API classification. 10.0 - 88.00 wt.-% of a base oil selected from special linear polyolefins with excellent low evaporation loss behavior at high temperatures, produced using metal catalysts of a kinematic viscosity in the range of 0.9 - 4.2, preferably 2.0 to 4.0 mm² / s at 100°C, particularly preferably 3.2 to 3.5 mm² / s according to Group IV of the API classification.

[0033] The additives may be, in particular, as follows: At least one of the 3 described boron-containing succinimide dispersants in a total concentration of 0.2-4.0 wt%, 0.1-3% of a boron-containing, ash-free dispersant based on poly-isobutylene succinimides (PIBSA or PIBSI) with a molecular weight MW of 500-1300, preferably 900-1100, particularly preferably 950-1050, prepared from maleamide and / or imide, an alkyl thiadiazole compound according to formula (1a) and / or (1b), in particular 1,3,4-thiadiazolidine-2,5-dithione, which are preferably obtained as reaction products of hydrogen peroxide and tert-nonanethiol.

[0034] The kinematic viscosity is determined according to the ASTM D445 test method. At -40°C, the viscosity is below 2000 mPas (measured according to DIN 51398), preferably even below 1500 mPas. The API classification of the oils is the classification of the American Petroleum Institute (API).

[0035] Information regarding the levels or concentrations of individual components provided within the scope of the invention refers to the entire lubricating fluid composition, unless otherwise stated.

[0036] The invention also relates to the use of the inventive lubricant composition in electronic components, such as battery-powered vehicles, electric drives, and high-speed transmissions in combination with electric machines. Copper and silver are regularly used in electronic components.

[0037] It also includes the possibility that the lubricant composition may contain further additives tailored to the base oil, such as anti-wear additives, antioxidants, metal deactivators, rust inhibitors, dispersants, friction modifiers and foam inhibitors.

[0038] Advantageously, the composition according to the invention allows the use of conventional flow improvers in comparatively low concentrations of only < 0.5 wt.%. This is because, in the prior art, so-called flow improvers (viscosity index (VI) improvers and pour point depressants), for example higher molecular weight thickeners, are normally added in amounts of 5 to 15 wt.% to modify the flow properties of the base oil.

[0039] The invention offers the advantage of eliminating the need for polysulfides, or using them only in small quantities, while still achieving good lubricating properties. This prevents or slows down chemical attack on copper, which is found in electric motors, batteries, etc.

[0040] The liquid composition according to the invention is characterized by excellent thermal conductivity properties when used as a cooling fluid and in gearboxes.

[0041] Furthermore, no or very little corrosion is observed with electrical and electronic components and lacquered copper wires used in the windings of electric motors and drive machines. At the same time, the lubricant composition ensures excellent lubrication of gears with very low drag losses due to very low friction coefficients in tribological contacts.

[0042] Advantageously, the fluid composition according to the invention exhibits good compatibility with elastomer materials and polyamides used in transmissions and drive trains (such as special radial shaft seals (RWDR) made from ACM), even at comparatively high speeds or high operating temperatures. Good compatibility also exists with uncoated copper wire materials.

[0043] Furthermore, there is sufficient chemical compatibility with comparatively sensitive sealing materials, such as silicone-containing liquid sealants, which can be achieved, among other things, by the targeted use of the claimed borated succinimides in combination with the P / S compounds.

[0044] In addition to its low viscosity of 1.5 to 3.1 mm² / s at 100°C (measured using ASTM D445) or below 2000 mPas at -40°C (measured according to DIN 51398), the composition according to the invention advantageously also exhibits a shear loss (viscosity after shear) of less than 5% according to ASTM D445. This advantageously precludes classification in the internationally valid SAE J 306 classification for gear oils (as of 2019), which currently defines only significantly higher viscosity levels (> 3.8 mm² / s at 100°C).

[0045] According to the invention, the liquid composition additionally comprises a phosphorus compound or phosphorus-sulfur compound according to formula (II):

[0046] This is an ammonium salt of the phosphorus compound according to formula (II), wherein at least one of the residues on the ammonium cation is a C12-C14 tert-alkyl residue.

[0047] Phosphorus compound according to formula (II) is the reaction product of 4-methyl-2-pentanol and diphosphorus pentasulfide, propoxylated and esterified with diphosphorus pentoxide and salted with amines with a C12-14-tert-alkyl group.

[0048] Furthermore, the liquid composition can contain up to 6 wt%, in particular 3 to 6 wt%, of a dispersing polymethacrylate. Polymethacrylates are esters of polymethacrylic acid esterified with, for example, alkyl alcohols such as C1-C4 alkyl, especially with methanol (leading to polymethyl methacrylate, PMMA).

[0049] In a preferred embodiment of the invention, the base oil also comprises a GTL base oil according to Group III of the API classification. This advantageously improves its applicability in electronic components. The grouping of base oils is shown in the exemplary embodiment in a table.

[0050] Preferably, the composition according to the invention comprises a flow improver (PPD) in an amount of < 0.5 wt%, wherein the flow improver is selected from hydrogenated polystyrene co-isoprene (HSI), ethylene-propylene copolymers (OCP), polyisobutylene (PIB), polyalkyl acrylates and methacrylates and their copolymers (PAMA), vinylpyrrolidone / methacrylate copolymers, polyvinylpyrrolidone, polybutenes, olefin copolymers, styrene / acrylate copolymers, polyethers, alkylated naphthalene derivatives, and mixtures thereof. Polyalkyl acrylates and methacrylates are particularly preferred.

[0051] In a preferred embodiment of the invention, the composition has a boron content of 20 to 300 mg / kg.

[0052] Preferably, the composition contains no or only small amounts of sulfur compounds of the type sulfurized olefins, from 0 to < 0.4%. These exhibit unfavorable corrosion behavior with copper alloys.

[0053] Preferably, the sulfur content in the lubricant composition according to the invention is 0.05 to 0.25 wt.%, particularly preferably 0.07 to 0.13 wt.%.

[0054] This sulfur content refers to the total content of the composition of bound and unbound sulfur, comprising sulfur contained in the sulfur compounds according to the alkyl thiadiazole compound of formula (I) and, optionally in a preferred embodiment, with the ammonium salt of a phosphorus compound according to formula (II). Any sulfur present in base oils and intermediate oils from additives is to be taken into account at 0.01 to 0.05 wt.% (PAO / GtL only residual sulfur). The sulfur content is a standard analytical parameter used in the quality assurance of gear oils.

[0055] In a preferred embodiment of the invention, the phosphorus content of the composition is 0.02 to 0.1 wt.%, particularly in the form of phosphorus bound in various additives. Here, "phosphorus content" refers to the total content of the composition of bound and unbound phosphorus, including any phosphorus present in the base oil as well as phosphorus bound in corresponding additives. Phosphorus-containing additives are known to improve the lubricity of the composition against abrasive wear.

[0056] In a preferred embodiment of the composition according to the invention, the kinematic viscosity measured at 100 °C is 1.5 to 3.3 mm² / s (centistokes), preferably 2.0 to 2.9 mm² / s, and particularly preferably 2.5 to 2.9 mm² / s. Viscosities in the aforementioned ranges are particularly suitable for the lubrication of gears in electric drives.

[0057] To modify the flow properties of the base oil, so-called flow improvers (viscosity index (VI) improvers and pour point depressants), for example, higher molecular weight thickeners in amounts of 5 to 15 wt.%, are normally added. The composition according to the invention preferably contains these classic flow improvers only in comparatively low concentrations of < 0.5 wt.%.

[0058] For a target viscosity of the finished lubricant of KV100 = 3cSt, or lower, a GTL 3 and possibly also a GTL 4 are particularly preferred (see Table 1). Table 1: KV 40 Flash Point GTL 3 Range: 6.5 - 11.0 >140°C Distillates (Fischer-Tropsch), heavy, C18-50-drifted, cyclic and linear GTL 4 17,2 >210°C EC / List no.: 482-220-0 CAS no.: 848301-69-9 Molecular formula: C123H252 Those: https: / / echa.europa.eu /

[0059] Synthetic base oils of groups III and IV, as specified in the American Petroleum Institute (API) "Base Oil Interchangeability Guidelines", can be used as the base oil for the lubricant composition according to the invention. API base oil groups I to V are shown in Table 3. Table 3: Base oil group 1< Sulfur (wt%) 2< and / or Saturated hydrocarbons (wt%) 3< Viscosity index 4< Group I > 0,03 and / or < 90 ≥ 80 to < 120 Group II ≤ 0,03 and ≥ 90 ≥ 80 to < 120 Group III ≤ 0,03 and ≥ 90 ≥ 120 Group IV all polyalphaolefins (PAOs) Group V all others not included in groups I to IV 1< Groups I to III are mineral oil base materials. 2< ASTM D1552, ASTM D2622, ASTM D3120, ASTM D4294 or ASTM D4927. 3< ASTM D2007 4< ASTM D2270

[0060] Further preferred embodiments of the invention result from the other features mentioned in the dependent claims.

[0061] Unless otherwise stated in individual cases, the various embodiments of the invention mentioned in this application can be advantageously combined with one another. Examples materials

[0062] Base oil: Syn 2.5: Chevron Synfluid 2.5 PAO 4: Polyalphaolefin 4 HC 3 / 4 Viscosity improvers: D-PMA: Dispersing polyalkyl methacrylate Dispersant: B-PP: borated PIBSA / PAM succinimide PP: boron-free PIBSA / PAM succinimide Extreme Pressure Additive: EP 1: AT: Alkyl-thiadiazole with C 9 H 19 (tert-nonyl); according to (1a) / (1b) EP 2: olefinic polysulfide Anti-wear additive: AW 1: Phosphoric acid compound (reaction product of 4-methyl-2-pentanol and diphosphorus pentasulfide, which is propoxylated, esterified with diphosphorus pentoxide and salted with amines and has a C12-14-tert-alkyl group; according to (II) AW 2: Alkyl phosphatamine salt AW 3: Irgalube ®< 353 (BASF) AW4: Alkyl phosphite AW5: Dibutylphosphonate AW6: Amine-neutralized phosphoric acid esters Friction improvers: FM 1 : Molybdenum dicarbamate FM 2: ethoxylated amine Corrosion protection additive: KS 1: Triazolalkylamine KS 2: Irgamet ®< TTZ (BASF) KS 3: Alkylbenzotriazolealkylamine Antioxidant: AO 1: Bisnonylphenylamine AO 2 : Diphenylamine Positioning oil Examples 1 to 10

[0063] Compositions according to Table 4 were produced by mixing, with all values ​​referring to wt.%.

[0064] The compositions of Examples 1 to 10 (Examples 4 to 10 are not covered by the invention) were investigated with regard to various physical and thermodynamic properties. The results are summarized in Tables 5 to 8.

[0065] The elemental composition of the compositions of Examples 1 to 10 is shown in Table 9, with all values ​​given in mg / kg of the total composition. Example 10 is a typical modern manual transmission oil with excellent lubricating properties; however, both its thermal stability and compatibility with copper are insufficient for applications in the electric drivetrain of an electric motor. Its efficiency also proved to be significantly lower. Table 4: Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Base oil Syn 2.5 76,3 95,3 95,7 79 75 70 70 52 78 PAO 4 20,0 10,0 14,0 19,0 21,0 43 14 HC 3 / 4 82,2 Viscosity compound D-PMA 0,3 0,3 0,3 8 Dispersant B-PP 1,5 1,5 0,5 3,6 3,6 3,6 3,6 1 0,5 1,5 PP 1,5 2,5 EP additive EP 1 0,30 0,30 0,33 0,5 0,8 1,5 EP 2 1,9 Wear protection AW 1 0,4 0,4 0,44 0,5 AW 2 2,7 1,8 1,3 + AW 3 0,5 AW 4 0,8 AW 5 0,5 0,5 0,5 0,5 AW 6 0,4 Corrosion protection KS 1 0,1 0,1 0,1 0,1 KS 2 0,1 KS 3 0,1 Friction coefficient increaser. FM 1 0,5 FM 2 0,3 Antioxidant AO 1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 AO 2 0,1 0,05 AO 3 0,05 Positioning oil 2 2 2,6 2 2 2 2 2 2 2 Table 5: test Unit Target value Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Dynamic viscosity at -40 °C (Brookfield) DIN 51398 mPas ≤ 1200 920 850 890 2420 1070 1010 1010 1100 950 10.000 at +40 °C ASTM D 445 mm 2< / s 11,5 10,2 9,5 11,3 11,6 11,6 11,7 11,8 11,6 27,4 at +100 °C ASTM D 445 mm 2< / s 3,1 + / - 0,1 3,1 2,9 2,7 3,0 3,1 3,1 3,1 3,1 3,1 6,0 Evaporation loss at 200 °C ASTM D 5800 wt.% ≤ 8,0 6,8 7,5 7,1 9,3 7,7 7,8 6,8 5,7 6,7 4,0 Copper tolerance after 70 hours at 160 °C PV1491 Copper strip evaluation Identification number ≤ 3 3 3 4B 1 2C 2A 2A 3B 4 4C Copper content in oil mg / kg < 50 10 9 17 160 92 26 12 2 31 180 Oxidation test 170 °C / 192 h CEC-L-48-A00 / B Blotter spot test drop area no solid / sticky residue no no no no no no no no no no Yes delta KV at 100 °C ASTM D 445 % ≤ 10 9,1 5,7 12,2 -1,4 -1,1 -0,6 -0,3 10,4 6,0 >20 Table 6: test Unit Target value Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Lubrication properties FZG A10 / 16.6R / 90 (SKS) FVA 243 SKS ≥ 9 9 10 10 8 6 6 5 7 7 11 FZG A10 / 33,2R / 90 (SKS) PV1816 ≥ 9 9 10 10 6 6 5 4 8 9 12 FZG S-A10 / 16.6R / 90 SKS ≥ 5 5 5 4 7 FZG C / 0.05:0.57 / 90:120 / 12 Ri + Ra mg Wear on the pinion mg < 20 33 30 4 13 Wheel wear mg < 40 114 25 1 8 FE8 rolling bearing properties (2 tests of 2 bearings each) Wear test according to DIN 51819-3 Weight loss roll set mg < 25 5 / 3 <2 / <2 3 / 2 7 / 6 5 / 5 9 / 7 8 / 9 Fatigue test PV 1483 Million in 200 hours 8,64 8,64 8,64 8,64 8,64 8,64 8,64 8,64 fail fail 8,64 Fuel Economy steady-state temperature PV 1454 Experimental oil °C 102 97 96 100 103 103 101 100 115 FVA Reference Oil 4% A 99 133 °C must be specified 133 133 133 133 133 133 133 133 133 133 efficiency advantage % 23 27 28 25 23 23 24 25 13 Table 8: test Unit Target value Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Loss factor IEC 60247 (800 VAC, 50 Hz) New oil at 23°C <1,0 0,6 0,6 New oil at 100°C ≤ 7,0 5,5 9,9 Permittivity IEC 60247 (100 kHz) New oil at 23°C ≤ 2,5 1,9 1,9 New oil at 100°C ≤ 2,5 1,8 1,8 heat capacity ASTM D7896-19 cP @40°C J / gK ≥ 2,10 2,12 2,11 2,12 2,11 2,11 2,11 2,0 cP @100°C J / gK ≥ 2,33 2,35 2,33 2,35 2,34 2,34 2,34 cP @150°C J / gK ≥ 2,56 2,58 2,55 2,60 2,59 2,59 2,59 2,23 Thermal conductivity properties ASTM D7896-19 Thermal conductivity @40°C mW / mK ≥ 140,0 142,4 141,3 142,5 142,0 141,5 141,3 139,1 Thermal conductivity @100°C mW / mK ≥ 131,0 133,7 131,5 133,1 132,9 132,6 132,5 131,1 Thermal conductivity @150°C mW / mK ≥ 124,0 126,3 122,9 126,2 125,8 125,5 125,4 124,3 Table 9: element Target value Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Ba <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 K <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Ti <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 V <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Ni <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Cu <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Sn <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Pb <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 W <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Li <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Co <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Cr <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Fe <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Al <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Mn <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Zn <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 N / a <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Mg <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Approx <5 <5 <5 <5 <5 <5 <5 30 70 800 B 20 to 300 177 176 56 181 170 167 180 33 65 135 N 0,07 0,07 0,06 0,25 0,16 0,14 0,13 0,05 0,12 0,098 Si 1 1 0 17 10 9 12 6 8 7 P 200 to 1000 240 240 270 2610 1770 1220 650 130 350 641 S 700 to 1300 1240 1210 1280 <20 <5 <5 <5 1060 2220 8600 Cl 19 18 4 3 4 5 5 5 54 35 Mon <5 <5 <5 <5 <5 <5 <5 <5 <5 250

Claims

1. Liquid composition having a kinematic viscosity in the range of 0.8 to 4.0 mm2 / s at 100°C, measured according to ASTM D445, comprising • 50-99.93 wt.% of a base oil or base oil mixture selected from polyalphaolefin oils according to Group IV of the API classification or GTL base oils according to Group III of the API classification; as well as the following additives: • 0.2 to 4.0 wt.% of a boron-containing, ash-free succinic acid amide and / or imide, • 0.05 to 1.0 wt.% of an alkyl thiadiazole compound according to formula (la) and / or (Ib), where C9H19 is tert-Nonyl, and • the following phosphorus compounds (II), obtained as a reaction product from 4-Methyl-2-pentanol and diphosphorus pentasulfide, which is propoxylated, esterified with diphosphorus pentoxide and salted with amines and has a C12-14-tert-alkyl group 2. Liquid composition according to any of claims 1 or 2, wherein the boron-containing, ash-free succinic acid amide and / or imide is a dispersant based on polyisobutylene succinamide or -imide (PIBSA or PIBSI) produced from maleic acid amide or imide.

3. Liquid composition according to any of claims 1 or 2, wherein the boron-containing, ash-free succinic acid amide and / or imide has a molecular weight MW of 500 to 1300, preferably 900 to 1100, particularly preferably 950 to 1050.

4. Liquid composition according to any of claims 1 to 3, wherein the alkyl thiadiazole compound according to formula (la) and / or (Ib) has a proportion of 0.2 to 0.8 wt.%.

5. Liquid composition according to any of claims 1 to 4, further comprising the thiophosphite EG 424-820-7.

6. Liquid composition according to any of claims 1 to 5, further comprising a flow improver in an amount of < 0.5 wt.%, wherein the flow improver is selected from hydrogenated polystyrene-co-isoprene (HSI), ethylene-propylene copolymer (OCP), polyisobutylene (PIB), polyalkyl acrylates and methacrylates and their copolymers (PAMA), vinylpyrrolidone / methacrylate copolymers, polyvinylpyrrolidone, polybutenes, olefin copolymers, styrene / acrylate copolymers, polyethers, alkylated naphthalene derivatives and mixtures thereof.

7. Liquid composition according to any of claims 1 to 6, wherein it has a boron content of 20 to 300 mg / kg.

8. Liquid composition according to any of claims 1 to 7, wherein the sulfur content is 0.05 to 0.25 wt.%, in particular 0.07 to 0.13 wt.%.

9. Liquid composition according to any of claims 1 to 8, wherein the phosphorus content is 0.02 to 0.1 wt.%.

10. Liquid composition according to any of claims 1 to 9, wherein the kinematic viscosity at 100°C is 2.0 to 2.8 mm2 / s, in particular 2.2 to 3.1 mm2 / s.

11. Use of the liquid composition according to any of claims 1 to 10 in battery-powered vehicles, electric drives and high-speed transmissions in combination with electric machines.

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