Base oil compositions, formulations and uses

Abstract

The present invention relates to a base oil. The base oil described herein is particularly useful in gear oil formulations, especially transmission fluids, and provides improved friction coefficient properties during use. More specifically, in some embodiments, gear oil formulations are provided that are particularly suitable for use in electric vehicles with or without integrated gearboxes.

Description

[Technical field]

[0001] The present invention relates to a base oil. The base oil described herein is particularly useful in gear oil formulations, particularly transmission fluids, and provides improved friction coefficient properties during use. More specifically, some embodiments provide gear oil formulations that are particularly suitable for use in electric vehicles with or without integrated gearboxes.

[0002] An electric vehicle is a vehicle that is propelled using one or more electric motors. Electric vehicles can be fully electric (also known as pure electric or all-electric vehicles) or hybrid in nature (in hybrid electric vehicles, propulsion can sometimes be achieved from alternative means such as hydrocarbon-derived fuels). Electric vehicles also include range-extended electric vehicles in which the vehicle is powered by an electric motor and a plug-in battery, although vehicles also include auxiliary combustion engines that are used only to supplement the battery charge and not as the primary propulsion source. The present invention is suitable for use in all of these types of electric vehicles.

[0003] Gear oil formulations are a subclass of lubricating oils and typically contain lubricating oil base stocks (or base oils) as their major component. The choice of lubricating base stock utilized in a lubricating oil can have a significant effect on properties such as oxidation and thermal stability, volatility, low temperature fluidity, ability to dissolve additives, contaminants, and decomposition products, and traction. The American Petroleum Institute (API) defines five groups of lubricant base stocks (API Publication 1509):

[0004] Groups I, II, and III are mineral oils classified by the amount of saturates and sulfur they contain and their viscosity index. Table 1 below illustrates these API classifications for Groups I, II, and III.

[0005] [Table 1]

[0006] Group I base stocks are solvent refined mineral oils, which are the cheapest base stocks to produce and currently account for most base stock sales. They provide satisfactory oxidation stability, volatility, low temperature performance, and traction properties, and have particularly good solvency for additives and contaminants. Group II base stocks are primarily hydrotreated mineral oils, which typically provide improved volatility and oxidation stability compared to Group I base stocks. The use of Group II stocks has grown to about 30% of the U.S. market. Group III base stocks can be highly hydrotreated mineral oils or produced by isomerization of wax or paraffins. They are known to have better oxidation stability and volatility than Group I and II base stocks, but have a limited range of commercially available viscosities.

[0007] Group IV base stocks differ from Groups I-III in that they are synthetic base stocks, e.g., polyalphaolefins (PAOs). PAOs have good oxidative stability, volatility, and low pour points. Drawbacks include moderate solubility of polar additives, e.g., anti-wear additives.

[0008] Group V base stocks are all base stocks not included in Groups I-IV. Examples include alkyl naphthalenes, alkyl aromatics, vegetable oils, esters (including polyol esters, diesters, and monoesters), polycarbonates, silicone oils, and polyalkylene glycols.

[0009] Gear oil formulations suitable for use in the automotive field desirably provide long-life oils with relatively high viscosity (relative to other lubricant application areas) for lubrication of rear axles and some transmission systems in vehicle powertrains. Additionally, final drives and driving accessories in agricultural and construction equipment may also require gear oils. More generally, gear oil formulations desirably also provide good oxidation stability and rust or corrosion inhibition properties. Typically, additives are provided to lubricant base oils to provide desirable gear oil formulations for their intended applications, and base oils that provide desirable properties by themselves are still sought after to limit the need for formulators to incorporate expensive additives and provide simpler formulations that are easier and faster to manufacture.

[0010] The rapid movement towards electrification of passenger vehicles has exceeded the understanding and specifications of OEMs and regulators of current gear oil specifications. Current generation hybrid and electric vehicles still use standard automatic transmission fluid (ATF) formulations that were not specifically designed for this application. Current gear oils do not meet the dynamic requirements of OEMs due to rapid advancements in electric vehicle technology, ATF base fluids, and adpacks.

[0011] Furthermore, thermal management of components in electric vehicles is becoming increasingly important. In vehicle batteries, thermal management is crucial to ensure safe running and use. Currently, much research is being done to explore immersion-cooled battery systems, where the battery is in direct contact with a dielectric cooling fluid. Fluids with high thermal properties, such as heat capacity and thermal conductivity, are therefore required for this application. Cooling of electronic power systems, such as electric motors and transmissions, is also required to keep them functioning effectively without overheating. Removing excess heat from electronic systems also helps to reduce electrical resistance and therefore improve efficiency. Thus, the thermal properties of base fluids suitable for use in electric vehicles are significantly different from those developed for use in automotive combustion engines.

[0012] Thus, despite the continued development of lubricant technology for transmissions and gearboxes in internal combustion engines, hybrids and electric vehicles, there remains a need for lubricant formulations with improved energy efficiency over the life of the lubricant. More specifically, there is a need for lubricant technology optimized and tailored to meet the requirements of electric vehicle gearboxes, which differ from those of traditional combustion engines. Thus, there remains an active need for new base oils that provide high performance in electric engines (especially low traction and high thermal conductivity) but are commercially viable for the electric vehicle passenger car market. Summary of the Invention

[0013] According to the present invention, there is provided a base oil comprising a compound of formula (I),

[0014] [ka] (I) During the ceremony, each R is independently selected from hydrogen, alkyl, or alkylcarbonyl, the alkyl group containing 1 to 24 carbons; m is an integer from 1 to 10; Base oils are provided in which X is an alkyl moiety having 1 to 20 carbon atoms, and X can be the same or different for m repeat units.

[0015] Gear oil formulations containing the base oils described herein are also provided.

[0016] According to an alternative embodiment of the present invention there is provided a method of improving energy efficiency in an electric vehicle comprising using a base oil according to the first aspect of the present invention in the powertrain.

[0017] According to a further embodiment of the alternative embodiment of the present invention there is provided a method of improving energy efficiency in an electric vehicle comprising using in the gearbox a gear oil formulation according to an aspect of the present invention.

[0018] Additionally, there is provided the use of the base oils described herein in a vehicle powertrain. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] It is understood that any upper or lower quantity or range limits used herein can be independently combined.

[0020] When describing the number of carbon atoms in a substituent (e.g., "C1-C6"), it will be understood that the number refers to the total number of carbon atoms present in the substituent, including any present in any branching groups. Additionally, when describing the number of carbon atoms in, for example, a fatty acid, this refers to the total number of carbon atoms, including the carbon atoms in the carboxylic acid and any carbon atoms present in any branching groups.

[0021] The term "functionality" as used herein with respect to a molecule or a portion of a molecule refers to the number of functional groups in that molecule or portion of a molecule. A "functional group" refers to a group in a molecule that can participate in a chemical reaction. For example, carboxylic acid groups, hydroxyl groups, and amine groups are all examples of functional groups. For example, a diacid (having two carboxylic acid groups) and a diol (having two hydroxyl groups) both have a functionality of two, and a triacid and a triol both have a functionality of three.

[0022] Thus, according to one embodiment of the present invention, there is provided a base oil comprising a compound of formula (I),

[0023] [ka] During the ceremony, each R is independently selected from hydrogen, alkyl, or alkylcarbonyl, the alkyl group containing 1 to 24 carbons; m is an integer from 1 to 10; Base oils are provided in which X is an alkyl moiety having 1 to 20 carbon atoms, and X can be the same or different for m repeat units.

[0024] The base oils containing the compounds of formula (I) provide fluids that exhibit low traction coefficients suitable for use in gear oil formulations and provide improved coefficients of traction properties during use. The base oils containing the compounds of formula (I) provide suitable thermal conductivity and viscosity properties, making them suitable for use in electric vehicle powertrains. More specifically, the thermal conductivity properties of the base oils of the present invention are more suitable for use in electric vehicles than known base oils and known esters belonging to groups I, II, III, and IV. Additionally, some embodiments of the present invention also exhibit improved oxidation stability.

[0025] The base oil may comprise a random or block copolymer. Suitably, the base oil may consist solely of compounds of formula (I).

[0026] In the compound of formula (I), m is an integer of 1 to 10, preferably, m is an integer of 1 to 8, more preferably, an integer of 1 to 6, and most preferably, an integer of 1 to 4.

[0027] The polarity in the compounds of formula (I) is influenced by the number of repeating units m and the number of carbons present in the alkyl portion of X, as described further below. If the polarity in the compounds of formula (I) is too great, the base oils of the present invention will have poor compatibility with other base oils and elastomeric materials (e.g., seals) and may also adversely affect the oxidative stability of the base oil.

[0028] In the compound of formula (I), X is an alkyl moiety which may be the same or different for each repeat unit of m, such that when m is an integer of 2 or more, X may independently be one or more alkyl moieties. In either case, X is the same or different for each repeat unit of m, and X is an alkyl moiety having 1 to 20 carbon atoms. Suitably, the alkyl moiety may be branched or straight chain, with straight chain being preferred. Preferably, X is an alkyl moiety containing 2 to 6 carbons, most preferably 2 to 4 carbons. In some particularly preferred embodiments, X is an alkyl moiety having 3 or 4 carbons. Thus, when m is 1, the compound of formula (I) comprises alkyl diol units having a central alkyl group, which central alkyl group preferably contains 2 to 4 carbons. However, more preferably, the compound of formula (I) comprises a poly(alkoxy ether) of repeating alkoxy units, and in this embodiment, in formula (I), m is an integer of 2 to 10, representing the number of repeating alkoxy units present in the compound. Thus, preferably, the base oil of the present invention comprises a compound of formula (I) comprising a poly(alkoxy ether) of repeating alkoxy units having an alkyl group containing 1-6 carbons, preferably 1-4 carbons, such alkyl groups providing an average molecular weight (g / mol) of the poly(alkoxy ether) units of less than 2000 (g / mol), preferably less than 1000 (g / mol), more preferably less than 650 (g / mol). Suitable repeating alkoxy units include ethylene oxide, propylene oxide, trimethylene oxide, butylene oxide, tetramethylene oxide, and pentylene oxide. In some embodiments, alkoxy groups having branched alkyl chains, such as 1,2-propylene oxide or 1,3-butanediol, may be preferred, in which the branched nature of the repeating alkoxy units in this embodiment may provide less optimal traction and thermal conductivity (although still acceptable for its intended use in electric vehicles) but may have advantages in terms of base oil pour point.

[0029] As mentioned above, preferably the compound of formula (I) comprises a polyalkoxy ether consisting of repeating alkoxy units. It should be understood that such polyethers can be derived from different means including ring opening polymerisation (ROP) of epoxides or cyclic ethers (e.g. ethylene oxide, propylene oxide, oxetane, tetrahydrofuran and dioxane), condensation of glycols or polyglycols (e.g. 1,3-propanediol) by means including acid catalysed dehydration, or Williamson etherification of glycols or polyglycols and alkyl halides. Thus, the polyalkoxy ethers can preferably be derived from epoxy alkanes such as ethylene oxide, oxetane or tetrahydrofuran, or from glycols such as 1,3-propanediol, in which case most preferably the compound of formula (I) comprises a polyalkoxy ether with linear alkyl segments. More specifically, polyethylene glycol (PEG) (polyethylene oxide), polytrimethylene ether glycol (PTriMEG) (polytrimethylene oxide), and polytetramethylene ether glycol (PTMEG) (polytetramethylene oxide) have surprisingly been found to provide high thermal conductivity values ​​relative to their viscosities and therefore are particularly preferred in the present invention as they provide base oils that are particularly suitable for use in electric vehicles.

[0030] Thus, the polyalkylene oxide may preferably be derived from ethylene oxide, 1,3-propanediol, 1,3-propylene oxide (oxetane), or 1,4-butylene oxide (tetrahydrofuran), in which case the compound of formula (I) most preferably comprises polyethylene glycol (PEG) (polyethylene oxide), polytrimethylene ether glycol (PTriMEG) (polytrimethylene oxide), and polytetramethylene ether glycol (PTMEG) (polytetramethylene oxide), which have been found to provide surprisingly high thermal conductivity values ​​relative to their viscosity. The incorporation of branched alkoxy groups, such as those derived from 1,2-propylene oxide, is also possible. In this case, the branched nature of the repeating alkoxy units derived from cyclic ethers may provide a base oil with less optimal thermal conductivity (although still acceptable for its intended use), but may have advantages in terms of base oil pour point.

[0031] Desirably, the compounds of formula (I) comprise poly(alkoxy ethers) composed of repeating alkyleneoxy units derived from renewable biosources. More specifically, the poly(alkoxy ethers) may be derived from bio-ethylene oxide, bio-tetrahydrofuran, and / or biosourced glycols, including ethylene glycol, 1,3-propanediol, and 1,4-butanediol, which may be produced from bioethanol derived from natural sources.

[0032] As indicated above, the compounds of formula (I) contain two R groups independently selected from hydrogen, alkyl, or alkylcarbonyl, where the alkyl contains 1 to 24 carbons, more preferably 5 to 18 carbons, and most preferably 6 to 12 carbons. Thus, the two R groups can be the same or different, allowing for enhanced tuning of the physical properties of the compound (and thus the base oil) by varying R in the compound. Preferably, at least one of the R groups is selected from alkyl or alkylcarbonyl, and more preferably, both R groups are selected from alkyl or alkylcarbonyl, i.e., R is preferably not hydrogen.

[0033] It should be understood by those skilled in the art that when the compounds of formula (I) are terminated with either alkylcarbonyl (to form esters) or alkyl (to form ethers), these groups can be added either during or as part of the polyether synthesis reaction stage, or they can be added later in a subsequent reaction step.

[0034] Suitably, R may be derived from an acid or alcohol or other suitable acylation or alkylation reactant capable of forming a bond as depicted in formula (I) with an alkoxy or polyalkoxy ether group as described above to provide the desired R group. More specifically, R may be derived from an acid or other reagent that can be combined with an alkoxy or polyalkoxy ether group as described above to provide the desired ester-linked terminal R group, where most preferably R is derived from a carboxylic acid, suitable carboxylic acids include keto acids, aliphatic carboxylic acids, alpha hydroxy acids, dicarboxylic acids including adipic acid, and the like. Alternatively and additionally, R may be derived from an alcohol or other reagent that can be combined with an alkoxy or polyalkoxy ether group as described above to provide the desired ether-linked terminal R group. Desirably, R may be derived from an acid or alcohol. More specifically, R may be derived from an alcohol, suitable alcohols include aliphatic alcohols, keto alcohols, aromatic alcohols, polyol alcohols, and the like.

[0035] Preferably, R is derived from an aliphatic carboxylic acid or alcohol, which may be saturated or unsaturated, straight or branched chain.

[0036] Preferably, the aliphatic carboxylic acid or alcohol is saturated, as this provides improved oxidative stability.

[0037] Preferably, the aliphatic carboxylic acid or alcohol is linear. Linear molecules provide improved traction and thermal conductivity compared to comparable branched molecules, but branching may improve pour point properties and therefore linear molecules are preferred in some situations (e.g., use in colder environments), but it may be beneficial to provide different R groups (one of which is branched and one of which is linear) or to provide a base oil comprising two or more compounds of formula (I) where at least one compound contains branching in its R group.

[0038] Desirably, the compounds of formula (I) include acids or alcohols derived from renewable biosources, for example, the acids may be carboxylic acids derived from vegetable fats and / or oils. Thus, preferably, the aliphatic carboxylic acids or alcohols may be fatty acids or fatty alcohols, as described above. The fatty acids or fatty alcohols may be saturated or unsaturated. The fatty acids or fatty alcohols may be straight-chained or branched. Preferably, the fatty acids or fatty alcohols are saturated and straight-chained. Naturally, fatty acids and fatty alcohols having an even number of carbons in their fatty chains are more abundant in nature and therefore more readily and cheaply available, and therefore these forms of fatty acids or fatty alcohols may be preferred, particularly those having C6, C8, C10, and C12 chain lengths. The fatty acids or fatty alcohols may be understood to contain medium chain fatty acids providing a C5-C18 alkyl moiety in the R group of formula (I). More preferably, the fatty chains contain 5-12 carbons, and most preferably, the fatty chains contain 6-10 carbons. Suitable fatty acids may be selected from one or more of the following: valeric acid, levulinic acid, caproic acid, enanthic acid, benzoic acid, cyclohexanecarboxylic acid, caprylic acid, 2-ethylhexanoic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, isostearic acid, and oleic acid. Suitable fatty alcohols may be selected from one or more of the following: methanol, ethanol, isopropanol, tert-butanol, higher linear and branched primary, secondary, and tertiary alcohols (including Guerbet alcohols, e.g., 2-ethylhexanol, oxo alcohols, terpene alcohols, and bio-based alcohols, e.g., those derived via reduction of natural fatty acids).

[0039] Preferably, the base oil has an average molecular weight (g / mol) of 200-1500, more preferably 250-1000, most preferably 300-700.

[0040] Suitably, the base oil has a pour point of about -10° C. to about -90° C. Preferably, the base oil has a pour point of less than -15° C.

[0041] Preferably, the base oil has a viscosity of 6 mm as measured using an Anton Paar SVM viscometer. 2 / sec~1500mm 2 / sec, preferably 7mm 2 / sec~900mm 2 / sec, more preferably 8mm 2 / sec~300mm 2 / sec, most preferably 9mm 2 / sec~150mm 2 3 / sec at 40°C.

[0042] Preferably, the base oil has a viscosity of 2 mm as measured using an Anton Paar SVM viscometer. 2 / sec~100mm 2 / sec, preferably 2mm 2 / sec~50mm 2 / sec, more preferably 2mm 2 / sec~20mm 2 / sec, most preferably 2mm 2 / sec~5mm 2 3 / sec at 100°C.

[0043] Suitably, the base oil has a coefficient of friction of less than 0.016, preferably less than 0.013, more preferably less than 0.0100, and most preferably less than 0.0090, measured using a mini traction machine (MTM) at 75°C, a load of 16 N and a slide to roll ratio (SRR) of 30%.

[0044] Suitably the base oil has a thermal conductivity greater than 0.131 W / mK at 40°C, preferably greater than 0.135 W / mK at 40°C, more preferably greater than 0.141 W / mK at 40°C, and most preferably greater than 0.151 W / mK at 40°C.

[0045] The present invention also provides a gear oil formulation comprising said base oil as described above. Gear oils can be considered lubricating fluids and may have utility in other areas as lubricants, even when heat transfer and traction are not important. The gear oil formulation may be suitable for use as industrial, automotive and / or marine gear oils for use in any type of transmission system. However, the gear oil formulation preferably provides a gearbox oil, more specifically an integrated gearbox oil suitable for use in electric vehicles, because the base oil described above provides advantageous heat transfer properties and desirable traction properties during use. Additionally, providing good thermal properties in the gear oil may enhance engine life.

[0046] Thus, the gear oil formulations according to the present invention include those suitable for use in electric vehicle powertrains. More specifically, the gear oil formulations are suitable for use in both gear systems that are integrated with electric motors and those that are not. Such systems include axles, differentials, and transmissions.

[0047] The gear oil formulation may, in some less preferred embodiments, consist solely of the base oil as described above. Alternatively and preferably, the gear oil formulation may comprise at least 1 wt.%, preferably at least 2 wt.%, more preferably at least 4 wt.%, even more preferably at least 5 wt.%, of the base oil, based on the total weight of the formulation. The gear oil formulation may comprise up to 50 wt.%, preferably up to 35 wt.%, more preferably up to 20 wt.%, of the base oil, based on the total weight of the formulation. Thus, the above base oils are advantageously blended or mixed with additional base oils to provide gear oil formulations, which allow the base oil of the present invention to be incorporated into additional base oils that may be less expensive or provide some alternative advantageous physical properties to the gear oil for use in the desired transmission system.

[0048] In one embodiment, the gear oil formulation is non-aqueous. However, it will be understood that the components of the gear oil formulation may contain small amounts of residual water (moisture) and therefore may be present in the gear oil formulation. The gear oil formulation may contain less than 5% by weight of water, based on the total weight of the formulation. More preferably, the gear oil formulation is substantially free of water, i.e., contains less than 2% by weight, less than 1% by weight, or preferably less than 0.5% by weight of water, based on the total weight of the formulation. Preferably, the gear oil formulation is substantially anhydrous.

[0049] In order to adapt the gear oil formulation for its intended use, the gear oil formulation may contain one or more of the following additive types: 1. Dispersants: for example, alkenyl succinimides, alkenyl succinic acid esters, alkenyl succinimides modified with other organic compounds, alkenyl succinimides modified by post-treatment with ethylene carbonate or boric acid, pentaerythritol, phenate-salicylates and their post-treated analogues, alkali metal or mixed alkali metal, alkaline earth metal borates, dispersions of hydrated alkali metal borates, dispersions of alkaline earth metal borates, polyamide ashless dispersants, etc., or mixtures of such dispersants. 2. Antioxidants: Antioxidants reduce the tendency of mineral oils to deteriorate in service, the deterioration being evidenced by oxidation products such as sludge and varnish-like deposits on metal surfaces and by an increase in viscosity. Examples of the antioxidant include 4,4'-methylene-bis(2,6-di-tert-butylphenol), 4,4'-bis(2,6-di-tert-butylphenol), 4,4'-bis(2-methyl-6-tert-butylphenol), 2,2'-methylene-bis(4-methyl-6-tert-butylphenol), 4,4'-butylidene-bis(3-methyl-6-tert-butylphenol), 4,4'-isopropylidene-bis(2,6-di-tert-butylphenol), 2,2'-methylene-bis(4-methyl-6-nonylphenol), 2,2'-isobutylidene-bis(4,6-dimethylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2, phenolic antioxidants such as 6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-l-dimethylamino-p-cresol, 2,6-di-tert-4-(N,N'-dimethylaminomethylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol), bis(3-methyl-4-hydroxy-5-tert-butylbenzyl)-sulfide, and bis(3,5-di-tert-butyl-4-hydroxybenzyl). Other types of antioxidants include alkylated diphenylamines (e.g., Irganox L-57, e.g., BASF), metal dithiocarbamates (e.g., zinc dithiocarbamate), and methylene bis(dibutyldithiocarbamate). 3. Anti-Wear Agents: As the name suggests, these agents reduce wear on moving metal parts. Examples of such agents include phosphates, phosphites, carbamates, esters, sulfur-containing compounds, and molybdenum complexes. 4. Emulsifiers: For example, linear alcohol ethoxylates. 5. Demulsifiers: For example, addition products of alkylphenols and ethylene oxide, polyoxyethylene alkyl ethers, and polyoxyethylene sorbitan esters. 6. Extreme pressure agents (EP agents): for example, zinc dialkyl dithiophosphates (primary alkyl, secondary alkyl, and aryl types), sulfurized oils, diphenyl sulfide, methyl trichlorostearate, chlorinated naphthalenes, fluoroalkyl polysiloxanes, and lead naphthenate. A preferred EP agent is zinc dialkyl dithiophosphate (ZnDTP), for example, as one of the co-additive components for antiwear hydraulic oil compositions. 7. Multifunctional additives: for example, sulfurized oxymolybdenum dithiocarbamate, sulfurized oxymolybdenum organic phosphorodithioate, oxymolybdenum monoglycehde, oxymolybdenum diethylate amide, amine-molybdenum complex compounds, and sulfur-containing molybdenum complex compounds. 8. Viscosity index improvers: for example, polymethacrylate polymers, ethylene-propylene copolymers, styrene-isoprene copolymers, hydrogenated styrene-isoprene copolymers, polyisobutylene, and dispersant type viscosity index improvers. 9. Pour point depressants: for example, polymethacrylate polymers. It is an advantage of the present invention that the pour points of the compounds of formula (I) are suitable for use as gearbox oils, however, embodiments utilizing relatively long chain linear molecules may benefit from the addition of a pour point depressant. Additionally, the presence of some alternative additives may adversely affect the pour point of the formulation, making the addition of a pour point depressant attractive. 10. Foam suppressors: for example, alkyl methacrylate polymers and dimethyl silicone polymers. 11. Friction Modifiers: include amides, amines, and partial aliphatic esters of polyhydric alcohols, and may include, for example, glycerol monooleate, oleylamide, and alternative friction modifiers available from Croda under the tradename "Perfad" or available from Nouryon under the tradename "Ethomeen."

[0050] Suitably, the gear oil formulation may contain at least 0.5 wt%, preferably at least 1 wt%, more preferably at least 5 wt%, of one or more additive types, based on the total weight of the formulation. The gear oil formulation may contain up to 30 wt%, preferably up to 20 wt%, more preferably up to 10 wt%, of one or more additive types, based on the total weight of the formulation.

[0051] Other additives may also be present in the gear oil of known functionality at levels of 0.01 to 30 wt%, more preferably 0.01 to 20 wt%, especially 0.01 to 10 wt%, based on the total weight of the gear oil. These may include detergents, corrosion inhibitors, rust inhibitors, and mixtures thereof. Corrosion inhibitors include sarcosine derivatives, such as Crodasinic O available from Croda Europe Ltd. Ashless detergents include carboxylic acid dispersants, amine dispersants, Mannich dispersants, and polymeric dispersants. Ash-containing dispersants include neutral and basic alkaline earth metal salts of acidic organic compounds. Additives may have two or more functional groups in a single material.

[0052] The additive(s) may be available in the form of a commercially available additive pack. Such additive packs vary in composition depending on the required use of the additive pack. Those skilled in the art may select a suitable commercially available additive pack for gear oil. An example of an additive pack that is particularly suitable for gear oil is Evogen 5201, e.g., Lubrizol, USA, which is specifically designed for use in electric vehicles.

[0053] The gear oil preferably comprises at least 0.05 wt.-%, more preferably at least 0.5 wt.-%, in particular at least 1 wt.-%, especially at least 1.5 wt.-% of further additives (additive pack), based on the total weight of the gear oil. The gear oil preferably comprises up to 15 wt.-%, more preferably up to 10 wt.-%, in particular up to 4 wt.-%, especially up to 2.5 wt.-% of further additives (additive pack), based on the total weight of the gear oil.

[0054] Notwithstanding the above examples, in order for a gear oil to be suitable for use in an electric vehicle, the selection of any additives should take into consideration copper compatibility (due to the requirements of electric motors) as well as providing or exhibiting low (but not necessarily zero) electrical conductivity; not all additives commonly utilized in combustion engine automotive engines are suitable for use in electric ah vehicle powertrain fluids.

[0055] Gear oils may have a kinematic viscosity according to ISO grades, which are defined as the midpoint kinematic viscosity of a sample at 40° C. in cSt (mm 2 The viscosity is specified in units of 1 / sec. For example, ISO 100 has a viscosity of 100±10 cSt and ISO 1000 has a viscosity of 1000±100 cSt. Gear oils preferably have a viscosity in the range of ISO 10 to ISO 1500, more preferably ISO 68 to ISO 680.

[0056] It is also envisioned that the base oil may find utility as a heat transfer fluid. Such a heat transfer fluid may provide a means of removing heat from a system. Such a system that requires or benefits from the use of a heat transfer fluid may be a mechanical system or an electrical system. The base oil of the present invention may be well suited for use as a heat transfer fluid in electrical systems, and more particularly, as a heat transfer fluid in electrical vehicles.

[0057] According to another embodiment of the present invention, there is provided a method for improving energy efficiency in an electric vehicle, comprising using a base oil according to the first aspect of the present invention in the powertrain of the electric vehicle. The base oil may be used in various systems in the powertrain, such as axles, differentials, transmissions, battery packs, and power electronics. The base oil has properties suitable for use in an electric vehicle powertrain, including traction, thermal, conductivity, and viscosity properties optimized for use in electric vehicles. In a further alternative, there is provided a method for improving heat removal from an electric vehicle powertrain, comprising using a base oil according to the first aspect of the present invention in the electric vehicle powertrain.

[0058] Additionally or alternatively, a method for improving energy efficiency in an electric vehicle is provided, comprising using a gear oil formulation according to an aspect of the present invention in a gearbox of the electric vehicle. More specifically, the method for improving energy efficiency in an electric vehicle comprises providing a base oil in the form of a gear oil formulation in an integrated gearbox. Thus, there is provided the use of the base oil or gear oil formulation as described herein in a vehicle powertrain, particularly in an electric vehicle powertrain, more particularly in an electric vehicle integrated gearbox. More specifically, the base oil or gear oil can be used in systems in the powertrain, such as axles, differentials, transmissions, battery packs, and power electronics.

[0059] The gear oil formulations according to the present invention include those suitable for use in electric vehicle powertrains. More specifically, the gear oil formulations are suitable for use in both gear systems integrated with and not integrated with electric motors. Such systems include axles, differentials, and transmissions. It should be noted that an electric vehicle may be provided with two or more electric motors. [Brief description of the drawings]

[0060] The invention will now be described with reference to the following examples and the accompanying drawings. [Figure 1] 1 shows MTM traction coefficient data for experimental and commercial samples at 40° C. [Diagram 2] 1 shows MTM traction coefficient data for experimental and commercial samples at 60° C. [Diagram 3] 1 shows MTM traction coefficient data for experimental and commercial samples at 75° C. [Figure 4] 1 shows MTM traction coefficient data for experimental and commercial samples at 100° C. [Diagram 5] 1 shows MTM traction coefficient data for experimental and commercial samples at 120° C.

[0061] material The following materials are utilized in this example: Valeric acid-C5:0 acid (e.g., Merck Life Science UK Limited) Capric-Caprylic Acid Blend - C8 / 10 Acid Blend (PALMERA A5608, e.g., KLK EMMERICH GmbH) Isostearic acid (Prisorine™ 3501, e.g., Croda) Isovaleric acid (e.g., Merck Life Science UK Limited) 2-Ethylhexanoic acid (2-EHA) (CAS number: 149-57-5, e.g., Acros Organics) Octanoic acid ALMERA A9808 (e.g. KLK EMMERICH GmbH) Polytetrahydrofuran with a molecular weight of 250 g / mol (PolyTHF 250, e.g., BASF) Polyethylene glycol with a molecular weight of 250 g / mol (PEG 250 Mw) Poly(ethylene glycol) octyl ether containing C8 alcohol + 14% 2EO and 86% 6EO 1,3 Propane Glycol (e.g., DuPont Tate & Lyle Bio Products) Group III Base Oil (Yubase 4) Group IV Base Oils (PAO 4) Conventional combustion engine base fluids based on monoesters (Priolube™ 1976, e.g., Croda) Conventional combustion engine base fluids based on saturated esters (Priolube 1937, e.g. Croda).

[0062] 1. Example In the following examples, base oils were prepared which were compounds according to formula (I) detailed in Table 1.

[0063] [Table 2]

[0064] In the example of diester compounds, these can be prepared by the esterification reaction of a suitable alkyl diol (e.g., 1,4-dibutanediol, or a poly(alkoxy ether) diol such as PolyTHF 250) with one or more suitable fatty acids (e.g., valeric acid or a capric-caprylic acid blend). Two molar equivalents of the desired fatty acid are mixed with one mole of the alkyl diol, optionally in the presence of a catalyst. The reaction mixture can be optionally heated under reduced pressure and / or in an inter atmosphere to facilitate the esterification reaction. The resulting diester compound product can then be subjected to further purification, if desired, to obtain the desired product.

[0065] In the example of mixed ether ester compounds, these may be prepared by a procedure involving acid catalyzed dehydration in the presence of a monoalcohol (e.g., octanol) by condensation of a glycol or polyglycol (e.g., 1,3-propanediol), with the ratio of reagents selected to give the desired average oligomer length (e.g., poly(ethylene glycol) octyl ether containing C8 alcohol + 2EO 14% and 6EO 86%). The etherification reaction is stopped once the desired degree of etherification or oligomer length is achieved. The partially ether-capped material (which may optionally include a mixture of mono-, di-ether, and non-ether-capped species) is isolated and then esterified on the free hydroxyl functionality with the desired carboxylic acid species. Optionally, mono-ether-capped species may also be produced by alkoxylation of selected alcohols, which may then be esterified to give the mixed ether ester-capped material.

[0066] In the example diether-capped embodiments, they may be prepared by condensation of glycols or polyglycols, such as 1,3-propanediol, by means including acid-catalyzed dehydration in the presence of a monoalcohol, such as octanol, where the etherification reaction is driven as close to completion as possible. The resulting product may then be subjected to further purification, if desired, to obtain the desired product. Optionally, the product may contain small amounts of monoether-capped and non-ether-capped species, which may be optionally removed, retained, or further reacted, which, if further reacted, may include acetylation alkylation with reagents such as acetic anhydride or alkyl halides to obtain products containing minimal free hydroxyl functionality.

[0067] 2. Testing The following tests were used to evaluate the properties of the example base oils.

[0068] 2.1 Oxidative stability was measured using an Anton Paar RapidOxy machine. 4 grams of sample is placed in a pressure vessel and charged with oxygen at 700 kPa before being heated to 140°C. The time taken for the pressure to drop by 10% is measured as the Oxidative Induction Time (OIT). This provides a relative measure of the resistance of the tested sample to oxidative degradation; the longer the OIT, the more oxidatively stable the sample.

[0069] 2.2 Kinematic viscosity was measured at 100°C and 40°C using an Anton Paar SVM viscometer.

[0070] 2.3 Thermal conductivity was measured using a Thermtest THW-L2 based on the hot wire transient method. To create a reliable average, ten data points were collected at temperatures of 40°C and 80°C, with the fluid allowed to settle for 5 minutes between each data point. The test power was set to give a measured output power of 70-90mW and a temperature rise of approximately 3°C, and the test time was set to 1 second.

[0071] 2.4 Pour point testing was performed on an ISL Mini Pour Point 5Gs to determine the minimum temperature at which the material will still flow which correlates to ASTM D97 and D2500.

[0072] 2.5 The coefficient of friction was measured using a Mini Traction Machine (MTM) and tests were performed on a PCS MTM 1. All specimens required to set up the MTM, as well as standard specimens supplied by PCS, were sonicated in heptane for 15 minutes three times using a Camsonix C940 ultrasonic bath, draining the heptane and then refreshing after each sonication. All specimens were dried using nitrogen before assembly in the MTM.

[0073] [Table 3]

[0074] The test profile shows a 0-100% Sliding to Rolling Ratio (SRR) at 16N and 41 data points are taken at a given temperature to create a traction curve, which is repeated at 40°C, 60°C, 75°C, 100°C, 120°C, and 150°C to show performance over a wide range of temperatures.

[0075] 3.Results 3.1 Oxidative stability. The oxidation stability test data for the example samples and the comparative Group III base oils are provided in Table 3 below. Samples with an OIT of at least 40 minutes are considered oxidatively stable, an acceptable result for base oils utilized in gear oil formulations. More specifically, samples with an OIT of greater than 60 minutes performed well in this test. The sample with the highest OIT was example sample 732 / 160 at 74.4 minutes.

[0076] [Table 4]

[0077] 3.2 Kinematic viscosity at 100°C and 40°C. Table 4 below shows that the viscosities of the samples were as expected and correlated well with the size of the molecules. For the example samples, the viscosity change between 40°C and 100°C was significantly less than the Group III comparative base oils. This is due to the high viscosity index of the example samples with some materials having a viscosity index of over 200. As can be seen from Table 4, the majority of the example base oils have a comparable viscosity to the Group III comparative materials at about 4 cSt at 100°C, allowing for a fair comparison of the traction data.

[0078] [Table 5]

[0079] 3.3 Thermal conductivity at 40℃ and 80℃. Table 5 below shows the increase in thermal conductivity of the example materials when compared to commercial base oils of Type Group III, Group, and current ester technology, Priolube 1937. Priolube 1937 was selected as the comparative ester in this case because it has a viscosity of 4 cSt. The increase in thermal conductivity is important for lower operating temperatures of gears and sensitive components such as motors, electronics, and batteries.

[0080] [Table 6]

[0081] The thermal conductivity of the example samples was consistently high, indicating that the base oil according to formula (I) provides a means to achieve reliable high thermal conductivity gear oils suitable for use in electric vehicles. The sample with the highest thermal conductivity of the materials tested is 732 / 160, but as shown above, it has a thermal conductivity of 57 mm at 40°C. 2 It has a relatively high viscosity of 13.65 mm2 / sec. Therefore, the use of this base oil in gear oil formulations may benefit from the inclusion of a viscosity modifier. The sample with the greatest thermal conductivity for viscosity at 40°C was 725 / 196, which has a viscosity of 13.65 mm2 / sec at 40°C.

[0082] 3.4 Pour Point. The pour point data of the samples are provided in Table 6 below. Example sample 851 / 003 provided the best pour point of all materials tested. This is believed to be the result of branching in the short R group derived from isovaleric acid. Comparative Group III base oils had a pour point of -15°C, which is believed to be the highest pour point temperature at which the base oil is suitable for use in gear oil formulations. However, example samples with higher pour point values ​​can still be utilized with the addition of pour point depressants. More specifically, samples with good thermal conductivity profiles but less than optimal pour points can still be advantageous for use as fluids in electric vehicle powertrains.

[0083] [Table 7]

[0084] 3.5 Coefficient of friction measured using MTM. The MTM traction data in Table 7 below shows a significant reduction in the coefficient of friction when compared to Group III base oils, with a measured slide-to-roll ratio of 30%, and the data obtained is consistent at temperatures of 40°C and 75°C, which are realistic operating temperatures that the fluids will experience when used in electric vehicles. Additionally, the friction data is graphed for temperatures ranging from 40°C to 120°C, as shown in Figures 1-5, where it can be seen that the sample materials outperform the comparative Group III, Group IV, and conventional ester materials in terms of their low traction properties. All materials tested had lower levels of traction than the reference materials. Of these, the lowest traction materials are Example Sample 725-198 and Example Sample 725 / 196, which means that both the diester and mixed monoester, monoether materials are capable of producing very low traction. The traction data at 75°C is believed to be the best test temperature for traction performance for the preferred gear oil application.

[0085] It can be noted that as the temperature increases to 100°C (as shown in Figure 4), Example Sample 851-003 begins to lose performance. This is believed to be due to the low viscosity (3 cSt) of this material, which means that it is unable to maintain a stable lubricant film at this temperature. At 120°C, Example Sample 851-003 begins to perform even worse, exhibiting higher traction than the comparative fluid at low slide-to-roll ratios. Above about 30% slide-to-roll ratio, the remaining Example samples still provide lower traction than the comparative fluid. 120°C is considered a high temperature for an in-use transmission fluid, and therefore Example Sample 851-003 is believed to still provide a desirable base oil for application areas that do not operate at such high temperatures.

[0086] [Table 8]

[0087] 4. Overview of Results Thus, the base oils described herein have been demonstrated to have the ability to improve the efficiency and performance of vehicles having electric motors by having lower traction (providing reduced friction) and therefore reduced power consumption, and also have increased thermal conductivity (compared to currently available commercial fluids), enabling the potential for higher motor speeds and increased component life when used as cooling fluids in electric vehicle powertrains, or alternatively in battery cooling applications.

[0088] As shown in Figures 1, 2, and 3 (which show traction curves at 40°C, 60°C, and 75°C, respectively), the base oil samples behaved as expected, with the coefficient of friction increasing with slide-to-roll ratio, a range of temperatures believed to be most critical with respect to the operation of electric vehicles. Over this critical temperature range, all of the sample materials show significant advantages when compared to commercial Group III base oils, Group IV base oils, and even when compared to a commercial low traction ester, Priorube 1976.

Claims

1. A base oil comprising two or more compounds of formula (I), 【Chemistry 1】 During the ceremony, each R is independently alkylcarbonyl, the alkyl group containing 1 to 24 carbons; m is an integer from 1 to 10; X is a linear alkyl moiety having 1 to 20 carbon atoms, X being the same or different for m repeat units; A base oil, wherein at least one compound contains branching in the R group.

2. 2. The base oil of claim 1, wherein X is a linear alkyl moiety containing from 2 to 6 carbons, and optionally X is a linear alkyl moiety containing from 2 to 4 carbons.

3. 3. The base oil of claim 1 or 2, wherein m is an integer from 1 to 4 and represents the number of repeating alkoxy units.

4. The compound of formula (I) comprises a polyalkoxy ether consisting of repeating alkoxy units, 4. A base oil according to any one of claims 1 to 3, optionally wherein the compound of formula (I) comprises polyethylene glycol (PEG) (polyethylene oxide), polytrimethylene ether glycol (PTriMEG) (polytrimethylene oxide), and / or polytetramethylene ether glycol (PTMEG) (polytetramethylene oxide).

5. The base oil of claim 1, wherein the alkyl of the alkyl carbonyl contains 5 to 18 carbons, optionally 6 to 12 carbons.

6. 6. The base oil of any one of claims 1 to 5, wherein R is derived from an acid, optionally R is derived from an aliphatic carboxylic acid, which is saturated or unsaturated, straight or branched chain.

7. 7. The base oil of claim 6, wherein the aliphatic carboxylic acid is saturated and / or the aliphatic carboxylic acid is linear.

8. A gear oil formulation comprising a base oil according to any one of claims 1 to 7.

9. 9. A gear oil formulation according to claim 8, wherein the gear oil formulation comprises at least 1 wt.%, preferably at least 2 wt.%, more preferably at least 4 wt.%, even more preferably at least 5 wt.% of base oil, based on the total weight of the formulation; and / or the gear oil formulation comprises up to 50 wt.%, preferably up to 35 wt.%, more preferably up to 20 wt.% of base oil, based on the total weight of the formulation; and / or the gear oil formulation comprises less than 5 wt.% of water, based on the total weight of the formulation.

10. 10. The gear oil formulation of claim 8 or 9, wherein the gear oil formulation comprises one or more of the following additive types: dispersants, antioxidants, antiwear agents, emulsifiers, demulsifiers, extreme pressure agents, multifunction additives, viscosity index improvers, pour point depressants, foam inhibitors, and friction modifiers.

11. 11. A gear oil formulation according to claim 10, wherein the gear oil formulation comprises at least 0.5 wt.%, preferably at least 1 wt.%, more preferably at least 5 wt.%, of the one or more additive types, based on the total weight of the formulation, and optionally the gear oil formulation comprises up to 30 wt.%, preferably up to 20 wt.%, more preferably up to 10 wt.%, of the one or more additive types, based on the total weight of the formulation.

12. The gear oil has a kinematic viscosity in the range of ISO 10 to ISO 1500, more preferably ISO 68 to ISO 680, and the ISO grade is the midpoint kinematic viscosity in cSt (mm ２ A gear oil formulation according to any one of claims 8 to 11, wherein the viscosity is 100 MPa (MPa) / sec.

13. 13. Use of a base oil according to any one of claims 1 to 7 or a gear oil formulation according to any one of claims 8 to 12 in electric vehicle powertrains.

14. 14. The use of claim 13, wherein the vehicle powertrain is an electric vehicle powertrain and / or the use is in a system within the powertrain, the system being selected from one of the following: an axle, a differential, a transmission, a battery pack, and power electronics.

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