Aqueous lubricating composition comprising gallate

Abstract

The present application relates to an aqueous lubricating composition comprising at least:-water; -at least one polyalkylene glycol; -at least one antifreeze compound selected from the group consisting of glycols, preferably alkylene glycols; glycerol; diglycerol; tripolyglycerol, and mixtures thereof; -at least one gallate ester; and-at least one pH adjusting additive enabling the pH of the lubricating composition to be maintained between (8) and (15). The present application also relates to the use of such an aqueous lubricating composition for lubricating and / or cooling moving parts in a mechanical system or as a hydraulic fluid. The present application finally relates to the use of at least one gallate as an additive for improving the tribological properties of an aqueous lubricating composition.

Description

Technical Field

[0001] The present invention relates to the field of lubricating compositions. These lubricating compositions can be used in different applications, in particular as hydraulic fluids, for lubricating and / or cooling various mechanical systems, such as rolling bearings, gear mechanisms, bearings or engines.

[0002] More particularly, the present invention aims to propose a new water-based lubricating composition. Background Art

[0003] Lubricating compositions, also called "lubricants", are generally used in mechanical systems to reduce friction between parts and thus protect them from wear. In addition to the phenomenon of wear, friction also hinders the relative movement between contacting parts and causes energy losses that are detrimental to the optimal operation of the mechanical system.

[0004] Lubricants are used in a variety of applications, for example in metalworking, in particular for metal deformation operations, in gas turbines or steam turbines in the aviation, shipping, rail transport and power generation sectors, in propulsion systems of motor vehicles, for example for the lubrication of rolling bearings, gear mechanisms, engines etc.

[0005] For example, in the field of lubricants for engines or transmissions of motor vehicles, the formulations of the lubricants are an important issue since they can influence the fuel consumption and thus the CO2 emissions by exerting an influence on the friction forces occurring between the various components of the motor vehicle.

[0006] Regardless of the target application, the most common lubricants are hydrocarbon-based lubricants, typically consisting of one or more base oils to which are usually combined various additives specifically designed to stimulate the lubricating properties of the base oils, such as friction modifying additives.

[0007] Furthermore, friction between moving parts generates heat and it may be necessary to ensure cooling of the mechanical system or machined parts in conjunction with lubrication. Such cooling is usually provided by a cooling fluid other than a hydrocarbon-based lubricant, such as air, an aqueous fluid such as water, or a mixture of water and glycol.

[0008] Today, the development of new lubricants has to take into account new constraints in order to avoid the use of toxic or potentially toxic solvents or to reduce their environmental impact and CO2 emissions. As a result, water-based formulations are gaining more and more attention.

[0009] Although water is an excellent cooling fluid, it does not possess the tribological properties required of a lubricant, especially in terms of reducing friction and protecting components from wear.

[0010] Water-based lubricating compositions supplemented by various additives have been studied. Typically, these aqueous lubricants are therefore composed of an aqueous fraction and an organic fraction.

[0011] For example, document US2012 / 0149616 proposes an aqueous lubricant which, in addition to water, contains water-soluble polyalkylene glycol, an emulsifier, an alkylene glycol or glycerol type antifreeze additive, an anticorrosion additive, a defoaming additive, and a friction reducing additive.

[0012] Reference may also be made to document EP 3 042 946, which proposes an oil- and emulsifier-free metalworking fluid comprising a cellulose-type polymer.

[0013] However, the use of organic compounds (polyalkylene glycols, organic surfactants, biocomponents) proposed so far for aqueous lubricants does not provide adequate lubrication properties under demanding conditions (conditions of high temperature and / or high pressure, demanding mechanical contact, high shear, etc.), also known as lubrication conditions at the “limit operating regime” (defined, for example, in the following literature: Manuel des Techniques de l'ingénieur, Introductionà la tribology, Part 2.1, Jean Frêne and Hamid Zaïdi, published on September 10, 2011 ). These aqueous lubricants can therefore lead to the formation of carbon deposits on machine components when used at extreme operating conditions.

[0014] The use of these aqueous lubricants therefore involves specific running-in conditions and material or component designs, which represents an obstacle to their widespread use as a replacement for conventional hydrocarbon-based lubricants.

[0015] It has also been proposed to use solid lubricant nanoparticles (nanodiamond, MoS2, WS3, graphite, etc.) suspended in an aqueous fluid in aqueous formulations. Unfortunately, the use of these solid particles is not without problems of stability, use and safety of the lubricant from a toxicological point of view.

[0016] Therefore, the aqueous lubricants proposed so far cannot compete with hydrocarbon-based lubricants.

[0017] There is thus still a need to be able to develop new additive systems that make it possible to impart to aqueous fluids satisfactory lubricating properties, especially under demanding conditions, and properties that are at least comparable to those obtained with conventional hydrocarbon-based lubricants.

[0018] For example, patent application WO 2021 / 1259851 proposes a new water-based lubricating formulation comprising glycerol and hypericin. Application WO 2021 / 259853 can also be cited, which proposes an aqueous lubricating composition comprising a polyalkylene glycol, an antifreeze compound and a phosphorus-containing compound. Summary of the invention

[0019] Disclosure of the Invention

[0020] The present invention aims in particular to propose a new aqueous lubricant having particularly advantageous tribological properties, in particular good friction reduction and anti-wear properties, enabling it to be used in applications imposing severe lubrication constraints, in particular under conditions of high shear stresses and pressures.

[0021] More particularly, the present invention, according to its first aspect, relates to an aqueous lubricating composition comprising at least:

[0022] -water;

[0023] - at least one polyalkylene glycol;

[0024] - at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; trimerglycerol, and mixtures thereof;

[0025] - at least one gallic acid ester; and

[0026] - at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15.

[0027] The term "aqueous composition" in the meaning of the present invention is understood to mean a composition comprising water as base fluid, in other words as main solvent. In particular, water preferably represents more than 35% by mass of the total mass of the lubricating composition.

[0028] In the remainder of the text, "aqueous lubricating composition" or "aqueous lubricant" refers to the lubricating composition according to the invention as defined above.

[0029] Gallic acid is naturally present in various plants and is known for its antioxidant, antitumor and antibacterial properties. In addition, certain gallic acid esters have been proposed in the agricultural food field (propyl gallate is known as the antioxidant "E310") or as antioxidant additives in vegetable oils (Lida A. Quinchia et al., Journal of Agricultural and Food Chemistry, 2011, 29, 12917-12924).

[0030] As far as the inventors are aware, the use of gallic acid esters in aqueous lubricants has never been proposed, let alone for the purpose of improving their tribological properties.

[0031] Contrary to all expectations, the inventors have found that the use of a specific combination of at least one antifreeze compound chosen from glycols, at least one gallic acid ester and at least one polyalkylene glycol makes it possible to obtain aqueous formulations having excellent tribological properties.

[0032] In particular, as shown in the examples below, it is possible to obtain lubricating fluids having improved tribological properties by supplementing an aqueous formulation comprising a mixture of water, at least one polyalkylene glycol, at least one pH regulating additive maintaining the pH of the formulation between 8 and 15 and at least one antifreeze compound of the glycol type with a gallic acid ester such as octyl gallate or lauryl gallate.

[0033] Advantageously, the aqueous lubricant according to the invention therefore has good properties in terms of friction reduction, in particular under severe conditions of use.

[0034] The present invention therefore relates to the use of at least one gallic acid ester as an additive for improving the tribological properties, in particular with regard to friction reduction, of an aqueous composition further comprising at least: water, at least one polyalkylene glycol, at least one antifreeze compound chosen from glycols, and at least one pH regulating additive for maintaining the pH of the composition between 8 and 15.

[0035] In particular, the aqueous lubricating compositions formulated according to the invention enable a reduction in wear and friction, which allows them to be considered "superlubricants", i.e. friction phenomena can be considered insignificant or even non-existent, even under severe lubrication conditions. This phenomenon of extreme reduction of wear and friction between moving mechanical parts is known by the English term "superlubricity".

[0036] The good tribological properties of the aqueous lubricating compositions according to the invention even under conditions of severe lubrication working conditions therefore enable them to be widely used. They are therefore proven to be suitable for use as lubricants for a variety of applications, in particular as hydraulic fluids or for lubricating and / or cooling various mechanical systems, in particular under severe lubrication conditions. They can thus be used in any system and any application to replace conventionally used lubricants, in particular hydrocarbon-based lubricants. Examples of application are given in the remainder of this article.

[0037] According to another of its aspects, the invention thus relates to the use of an aqueous lubricating composition according to the invention for lubricating and / or cooling moving parts in a mechanical system, for example for lubricating and / or cooling a mobile or stationary motorisation system or as a hydraulic fluid.

[0038] The application also relates to the use of the aqueous lubricating composition according to the invention for reducing the friction between moving parts in a mechanical system, and the use of the aqueous lubricating composition according to the invention for reducing the wear of parts in a mechanical system.

[0039] For example, the aqueous lubricant according to the invention can be used to reduce friction and / or wear of moving parts in mobile or stationary motorized systems, for example at the transmission part of a vehicle's propulsion system.

[0040] The aqueous lubricant according to the present invention can also be used to reduce friction and / or wear of various components (especially metal components) in hydraulic systems.

[0041] Advantageously, the composition according to the invention combines good cooling properties associated with the presence of water with good tribological properties, in particular friction reduction and anti-wear properties. Thus, the aqueous composition according to the invention can advantageously ensure the dual function of lubrication and cooling.

[0042] The aqueous composition according to the invention can thus be used to avoid the use of two different fluids: a cooling fluid on the one hand and a lubricating fluid on the other hand.

[0043] Furthermore, the composition according to the invention has the advantage of being easy to formulate. Advantageously, it also has good anti-corrosion properties.

[0044] Finally, the gallic acid ester used in the composition according to the invention may advantageously be of bioorigin. "Biogenic" means any component of plant or animal origin, preferably of plant origin.

[0045] The lubricating composition according to the invention, which is formed predominantly from water and comprises at least one additive of biological origin, thus meets the desire to reduce the use of environmentally harmful substances while achieving lubricating properties comparable to conventional oil-based lubricants.

[0046] Finally, the aqueous lubricating composition according to the invention advantageously has a very good ability to dissolve the various compounds it comprises, in particular the antifreeze compound(s), the gallic acid ester(s) and the polyalkylene glycol(s).

[0047] Other characteristics, variants and advantages of the aqueous lubricating composition according to the invention will become more apparent on reading the following description and the examples, which are given by way of illustration and do not limit the invention.

[0048] The expressions “between ... and ...,” “from ... to ...,” “formed from ... to ...,” and “variant from ... to ...” are to be understood as including the limit values, unless otherwise indicated.

[0049] In the description and examples, unless otherwise indicated, the percentages are percentages by weight. The percentages are therefore expressed in mass relative to the total mass of the composition.

[0050] Detailed instructions

[0051] Aqueous composition

[0052] As described above, the aqueous lubricating composition (also referred to as aqueous lubricant) according to the present invention is a formulation containing water as a main solvent.

[0053] For the purposes of the present invention, "main solvent" is understood to mean that water is present in an amount greater than any other solvent that may be present in the composition. Preferably, the aqueous lubricating composition according to the invention comprises at least 20% by mass, preferably at least 30% by mass, in particular 35% to 90% by mass, more preferably 40% to 75% by mass of water, in particular deionized water, relative to the total mass of the composition.

[0054] Through its role as solvent, water makes it possible to dissolve the one or more polyalkylene glycols, the one or more antifreeze compounds of glycol type and the one or more gallic acid esters, at the desired pH of the composition, and any additives optionally present in the composition, in particular chosen from those additives detailed in the rest of the text.

[0055] Advantageously, in addition to its role as solvent, water makes it possible to obtain a lubricating composition having good cooling properties and which can be used as a cooling fluid for moving parts in mechanical systems.

[0056] According to a particular embodiment, the water used in the aqueous lubricating composition according to the invention is osmotic water or demineralized water, more preferably deionized water.

[0057] The term "permeate water" within the meaning of the present invention is understood to mean water which has been purified, in particular by reverse osmosis, to reduce the content of organic and / or mineral compounds, for example to a content below 5.0% by weight, preferably below 1.0% by weight. In the remainder of this text, the expressions "demineralized water" or "ultrapure water" will be considered equivalent or synonymous with the expression "permeate water". In particular, permeate water may be "deionized water", in other words water which has been purified to reduce the content of ions such as Ca, 2+ and HCO3 - Preferably, deionized water contains no ions.

[0058] Therefore, the use of deionized water is particularly advantageous when the aqueous lubricant according to the invention is used in applications requiring a fluid that is less conductive or even completely non-conductive, for example when the aqueous lubricant is used for lubrication and cooling of mechanical systems including electrical circuits, such as electric or hybrid engines, in particular in electric or hybrid vehicles.

[0059] The aqueous lubricating composition according to the invention thus differs from the lubricants conventionally used in mechanical systems, which comprise a major proportion of one or more water-insoluble base oils.

[0060] “Water-insoluble oil” is understood to mean in particular an oil which is substantially insoluble in water at ambient temperature (about 25° C.). In particular, a water-insoluble oil has a solubility in water of less than 0.2 g / L at ambient temperature.

[0061] This relates in particular to lubricating base oils belonging to groups I to V according to the categories defined in the API classification (or their equivalents according to the ATIEL classification), and mixtures thereof.

[0062] Preferably, the aqueous lubricating composition according to the present invention contains less than 5% by mass, preferably less than 2% by mass and more preferably less than 1% by mass of water-insoluble oil relative to the total mass of the composition.

[0063] Advantageously, the aqueous lubricating composition according to the invention is completely free of water-insoluble oils.

[0064] Polyalkylene glycol

[0065] As mentioned above, the aqueous lubricating composition according to the present invention comprises at least one polyalkylene glycol.

[0066] The polyalkylene glycol (denoted as "PAG") is selected from water-soluble polyalkylene glycols.

[0067] The term "water-soluble" refers to a polyalkylene glycol having a solubility in water at ambient temperature (about 25°C) of at least 10 g / L, preferably at least 500 g / L.

[0068] The polyalkylene glycols may more particularly be formed from C1-C4, preferably C1-C3 and more particularly C2-C3 alkylene oxide units.

[0069] Advantageously, the polyalkylene glycol used in the aqueous lubricating composition according to the invention comprises at least 50% by mass, in particular at least 80% by mass, more preferably at least 90% by mass of propylene oxide and / or ethylene oxide units. It may be a copolymer of ethylene oxide / propylene oxide, optionally a random copolymer.

[0070] Preferably, the polyalkylene glycol used in the aqueous lubricating composition according to the present invention has a weight average molecular weight (Mw) between 100 and 50000 g.mol -1 Between, preferably between 5000 and 25000 g.mol -1 between.

[0071] The weight average molecular weight can be measured by gel permeation chromatography (GPC).

[0072] Preferably, the polyalkylene glycol used in the aqueous lubricating composition according to the present invention has a kinematic viscosity (KV100) measured at 100° C. according to ASTM D445 standard between 100 and 25000 mm 2 / s, especially between 150 and 10000mm 2 / s.

[0073] Preferably, the polyalkylene glycol used in the aqueous lubricating composition according to the present invention has a kinematic viscosity (KV40) measured at 40° C. according to ASTM D445 standard between 500 and 100,000 mm 2 / s, more particularly between 1000 and 95000 mm 2 / s.

[0074] The flash point of the polyalkylene glycol used in the aqueous lubricating composition according to the invention is preferably higher than or equal to 160° C., in particular higher than or equal to 220° C. The flash point can be measured by ISO 2592 or ASTM D92 standards.

[0075] Preferably, the polyalkylene glycol used in the aqueous lubricating composition according to the invention has a viscosity index measured according to the ASTM D2270 standard of between 100 and 800, preferably between 250 and 550.

[0076] In particular, the one or more polyalkylene glycol compounds may be used in the aqueous lubricating composition according to the present invention in an amount of at least 5.0% by mass, preferably 5.0% to 50% by mass, more preferably 10% to 40% by mass, and particularly 10% to 20% by mass, relative to the total mass of the composition.

[0077] It should be understood that the aqueous lubricating composition according to the present invention may comprise a single polyalkylene glycol or a mixture of a plurality of different polyalkylene glycols.

[0078] In particular, the aqueous lubricating composition according to the invention may comprise a mixture of at least two different polyalkylene glycols, more particularly a mixture of at least one polyalkylene glycol of low weight average molecular weight and at least one polyalkylene glycol of high weight average molecular weight.

[0079] It is within the ordinary skill of those skilled in the art to adjust the nature and amount of the low and high weight average molecular weight polyalkylene glycols in the polyalkylene glycol mixture, particularly taking into account the target viscosity of the final lubricating composition.

[0080] The combination of at least one polyalkylene glycol of low weight average molecular weight and at least one polyalkylene glycol of high weight average molecular weight is particularly advantageous in order to obtain good solubilization of the various compounds introduced into the aqueous lubricating composition.

[0081] Antifreeze Compound

[0082] As mentioned above, the aqueous lubricating composition according to the present invention comprises at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof.

[0083] These compounds are known for their antifreeze effect, in other words they can be used to lower the freezing temperature of the composition.

[0084] Diols are diols in which the two hydroxyl groups are carried by different carbon atoms, preferably by adjacent carbon atoms.

[0085] Preferably, the diol is an alkylene glycol, in particular having 2 to 10 carbon atoms, in particular 2 to 6 carbon atoms. For example, mention may be made of monoethylene glycol, diethylene glycol and propylene glycol.

[0086] The antifreeze compound may also be selected from glycerol, diglycerol, triglycerol and mixtures thereof.

[0087] Preferably, the antifreeze compound used according to the invention is selected from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof. Preferably, the antifreeze compound is diethylene glycol.

[0088] In particular, the one or more antifreeze compounds may be used in the aqueous lubricating composition according to the invention in a content of at least 5.0% by mass, preferably between 5.0% and 45% by mass, more preferably between 10% and 35% by mass, in particular between 20% and 35% by mass, relative to the total mass of the composition.

[0089] Gallic acid ester

[0090] The aqueous lubricating composition according to the invention comprises at least one gallic acid ester.

[0091] The gallic acid ester or esters are advantageously used in a form which is soluble or emulsifiable in water, in particular in the form of ionic salts.

[0092] It is to be understood that the lubricating composition according to the invention may comprise a single gallic acid ester or a mixture of at least two different gallic acid esters.

[0093] In the meaning of the present invention, gallic acid esters are understood to mean esters formed between gallic acid and at least one alcohol.

[0094] The gallic acid ester may comprise multiple ester functional groups resulting from the reaction of the carboxylic acid functional groups of gallic acid with the multiple hydroxyl functional groups of an alcohol.

[0095] The gallic acid ester may thus be a monoester or a polyester, in particular a diester or a triester, of gallic acid.

[0096] In particular, a gallic acid ester may be formed between gallic acid and at least one monohydric alcohol or polyhydric alcohol (eg, a monohydric alcohol or a diol).

[0097] The term "monohydric alcohol" is understood within the meaning of the present invention to mean a compound formed by a hydrocarbon chain of alkyl or alkenyl type carrying a single alcohol function, in contrast to a "polyol" comprising at least two alcohol functions.

[0098] It may preferably be an ester formed between gallic acid and one or more monohydric alcohols.

[0099] The one or more identical or different monohydric alcohols preferably contain 1 to 24 carbon atoms, preferably 3 to 20 carbon atoms, in particular 3 to 18 carbon atoms, more preferably 6 to 16 carbon atoms, for example 8 to 14 carbon atoms.

[0100] Preferably, the one or more monohydric alcohols are linear monohydric alcohols, especially saturated.

[0101] Gallic acid esters suitable for use in the present invention may more particularly correspond to the following formula (I):

[0102]

[0103] wherein R represents a saturated, mono- or polyunsaturated, linear or branched hydrocarbon chain, preferably a linear and saturated hydrocarbon chain, having C1-C 24 , preferably C3-C 20 , more preferably C3-C 18 , especially C6-C 16 , such as C8-C 14 .

[0104] In a particular embodiment, the gallic acid ester according to the invention is obtained from gallic acid and a monohydric alcohol selected from 1-propanol, 1-butanol, 1-octanol and 1-dodecanol, in particular from 1-octanol and 1-dodecanol.

[0105] Advantageously, the gallic acid ester according to the invention is chosen from octyl gallate, lauryl gallate and mixtures thereof.

[0106] According to one particular embodiment, the aqueous lubricating composition according to the invention comprises at least lauryl gallate as gallic acid ester.

[0107] According to one particular embodiment, the aqueous lubricating composition according to the invention comprises at least octyl gallate as gallic acid ester.

[0108] In a particular embodiment, the aqueous lubricating composition according to the invention may use a single gallic acid ester, in particular lauryl gallate or octyl gallate, preferably lauryl gallate.

[0109] The gallic acid esters used according to the invention may be commercially available or prepared according to synthesis methods known to those skilled in the art. These synthesis methods more particularly implement an esterification reaction between at least one hydroxyl function of an alcohol and the carboxylic acid function of gallic acid.

[0110] The one or more gallic acid esters may advantageously be of biosource, ie they may be obtained from biomass.

[0111] The aqueous lubricating composition according to the invention may comprise 0.001-10% by mass, preferably 0.01-5% by mass, more preferably 0.1-2% by mass of the one or more gallic acid esters, in particular as defined above, relative to the total mass of the composition.

[0112] pH Adjusting Additives

[0113] The aqueous lubricating composition according to the invention comprises at least one pH-adjusting additive, more particularly a “basic buffer”, which makes it possible to maintain an alkaline pH of the lubricating composition.

[0114] The pH regulating additive or additives more particularly make it possible to maintain the pH of the lubricating composition between 8 and 15.

[0115] The one or more pH regulators make it possible in particular to prevent corrosion of metal surfaces by ensuring that the pH of the aqueous lubricating composition is maintained between 8 and 15, but can also promote the solubilization of the different compounds, in particular the one or more polyalkylene glycols, the one or more antifreeze compounds and the one or more gallic acid esters, in particular as defined above, in the lubricating composition.

[0116] Advantageously, the pH regulating additive(s) make it possible to maintain the pH of the aqueous lubricating composition between 8.5 and 14, more particularly between 9 and 13, or between 8 and 11.

[0117] In particular, the one or more pH adjusting additives are chosen from amines, more particularly from alkanolamines and amino alcohols.

[0118] As pH adjusting additives, there may be mentioned alkanolamines such as dimethylethanolamine (DMEA), ethanolamines such as monoethanolamine (MEA), diethanolamine (DEA); triethanolamine (TEA), isopropanolamines such as monoisopropanolamine (MIPA), diisopropanolamine (DIPA) and triisopropanolamine (TIPA), diglycolamine (DGA), ethyleneamines such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA); cyclic amines such as cyclohexylamine, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1-propanol and mixtures thereof.

[0119] Preferably, the one or more pH adjusting additives are selected from alkanolamines, in particular ethanolamines, more particularly dimethylethanolamine (DMEA), triethanolamine (TEA) and mixtures thereof, more particularly dimethylethanolamine.

[0120] It will be appreciated that the composition may comprise one or more pH adjusting additives which enable the desired pH of the aqueous lubricating composition to be maintained.

[0121] According to one particular embodiment, the aqueous lubricating composition according to the invention comprises, as pH-adjusting additive, at least one alkanolamine, in particular dimethylethanolamine (DMEA) and / or triethanolamine (TEA).

[0122] According to another embodiment, the aqueous lubricating composition according to the invention comprises ethanolamine, in particular triethanolamine (TEA), as pH adjusting additive.

[0123] The aqueous lubricating composition according to the invention may especially comprise 0.1% to 10% by mass, preferably 0.5% to 5% by mass, relative to the total mass of the composition, of a pH regulating additive making it possible to maintain the pH of the composition between 8 and 15, in particular as defined previously, especially chosen from alkanolamines.

[0124] The aqueous lubricating composition according to the invention may optionally comprise, in addition to at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15 (in particular as defined previously), one or more different pH regulating additives, called “auxiliary pH regulating additives”.

[0125] In this case, it will be appreciated that the nature and amount of the auxiliary pH adjusting additive is chosen so as not to affect the overall pH of the aqueous lubricating composition which is maintained between 8 and 15 due to the presence of said pH adjusting additive as previously described.

[0126] According to a particular embodiment, the aqueous lubricating composition according to the invention may comprise at least:

[0127] - at least 35% by weight of water, in particular deionized water;

[0128] - 5.0% to 50% by mass of at least one polyalkylene glycol, in particular as defined above;

[0129] -5.0% to 35% by weight of at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; preferably diethylene glycol;

[0130] - 0.001% to 10% by mass of at least one gallic acid ester, in particular as defined above, especially lauryl gallate; and

[0131] - 0.1% to 10% by mass of at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15, in particular as defined above, especially chosen from alkanolamines.

[0132] Other additives

[0133] The aqueous lubricating composition according to the present invention may further contain various other additives.

[0134] It will be appreciated that the additives are compatible with their use in aqueous media. Advantageously, the additives are used in a water-soluble or water-emulsifiable form, for example in the form of an ionic salt or a liquid.

[0135] The additives are of course selected for the intended application of the aqueous lubricant.

[0136] Of course, a person skilled in the art will be aware of selecting possible additives and / or their amounts so that the advantageous properties of the aqueous lubricating composition according to the invention (in particular the tribological properties, especially the properties of reducing friction and protecting parts from wear, and the cooling properties) are not adversely affected by the proposed addition of additives.

[0137] Such additives may more particularly be chosen from defoamers, biocides, corrosion inhibitors, antiwear and / or extreme pressure additives, chelating agents, metal deactivators, colorants, dispersants, emulsifiers and mixtures thereof.

[0138] Advantageously, the aqueous lubricating composition according to the invention may comprise one or more additives selected from defoamers, corrosion inhibitors, metal deactivators, colorants and mixtures thereof.

[0139] The aqueous lubricating composition according to the invention may more particularly comprise 0.1% to 10% by mass, more preferably 1.0% to 8.0% by mass of additives relative to the total mass of the composition.

[0140] Corrosion Inhibitors

[0141] The aqueous lubricating composition according to the invention may contain at least one corrosion inhibitor. Corrosion inhibitors advantageously make it possible to reduce or even prevent corrosion of metal parts. The nature of the corrosion inhibitor may be chosen according to the metal to be protected against corrosion, for example aluminum, steel, galvanized steel, yellow metals such as copper or brass.

[0142] Among the inorganic corrosion inhibitors, mention may be made of nitrites, sulfites, silicates, borates, sodium, potassium, calcium or magnesium phosphates, alkali metal phosphates, hydroxides, molybdates, zinc, magnesium or nickel sulfates.

[0143] Among the organic corrosion inhibitors, mention may be made of alkanolamines such as triethanolamine, aliphatic monocarboxylic acids having in particular 4 to 15 carbon atoms such as octanoic acid, aliphatic dicarboxylic acids having in particular 4 to 15 carbon atoms such as sebacic acid, undecanedioic acid, dodecanedioic acid or mixtures thereof, polycarboxylic acids optionally neutralized with triethanolamine such as 1,3,5-triazine-2,4,6-tris-(6-aminohexanoic acid), alkanoylamidocarboxylic acids, in particular isononanoylamidocaproic acid and mixtures thereof. Boric acid amides resulting from the reaction of amines or amino alcohols with boric acid may also be used.

[0144] Preferably, said corrosion inhibitor is different from said pH regulating additive, which additive makes it possible to maintain the pH of the lubricating composition between 8 and 15 and is as previously defined.

[0145] The aqueous lubricating composition according to the present invention may contain in particular 0.1% to 5% by mass, preferably 0.5% to 4% by mass, more preferably 1% to 2.5% by mass of a corrosion inhibitor relative to the total mass of the composition.

[0146] In a particular embodiment, the aqueous lubricating composition according to the invention comprises at least:

[0147] -water;

[0148] - at least one polyalkylene glycol;

[0149] - at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; trimerglycerol, and mixtures thereof;

[0150] - at least one gallic acid ester, in particular as defined above;

[0151] at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15, in particular as defined above, especially chosen from alkanolamines; and

[0152] - at least one corrosion inhibitor, in particular at least one organic corrosion inhibitor, more particularly chosen from aliphatic monocarboxylic acids.

[0153] Anti-wear / extreme pressure additives

[0154] The aqueous lubricating composition according to the invention may contain at least one antiwear and / or extreme pressure additive. Their function is to reduce the wear and friction coefficients or to prevent metal-metal contacts by forming an adsorbed protective film on these surfaces.

[0155] There is a wide variety of antiwear additives, among which mention may be made of those selected from phosphorus-sulfur additives such as metal alkylthiophosphates or their salts.

[0156] Additives which do not provide phosphorus may also be suitable, such as polysulfides and particularly sulfur-containing olefins.

[0157] According to a particular embodiment, the aqueous lubricating composition according to the invention comprises at least one extreme pressure additive chosen from sulphur-containing fatty acids and dimercaptothiadiazoles, preferably used in its neutralized, water-emulsifiable or water-soluble form. Advantageously, the aqueous lubricating composition according to the invention comprises at least one extreme pressure additive of the sulphur-containing fatty acid type, preferably in neutralized form, in particular by an inorganic alkalizing agent or an alkanolamine.

[0158] The sulphur-containing fatty acids may contain 8 to 22 carbon atoms, in particular 12 to 18 carbon atoms.

[0159] The amount of sulfur provided by the sulfur-containing fatty acid according to ASTM D2622 standard may be 5% to 30% by mass, in particular 10% to 20% by mass.

[0160] Preferably, the amount of active sulfur at 150° C. provided by the sulfur-containing fatty acid in the aqueous lubricating composition according to the present invention according to ASTM D1662 is greater than or equal to 2% by mass, particularly 5-10% by mass, relative to the total mass of the lubricating composition.

[0161] The term "active sulfur" in the meaning of the present invention is understood to mean the sulfur that a compound is able to generate or release when it is subjected to the conditions of the ASTM D1662 standard. The ASTM D1662 standard defines the active sulfur content of a compound at a given temperature as the difference in weight percentage between the sulfur content before and after a sample of the sulfur-containing compound is reacted with a given amount of copper for a fixed time.

[0162] The amount of active sulfur at 150°C (ASTM D1662 standard) in the aqueous lubricating composition of the present invention can affect its extreme pressure performance. This amount of active sulfur at 150°C (ASTM D1662 standard) in the lubricating composition cannot be too low, otherwise satisfactory extreme pressure performance cannot be obtained. It cannot be too high either, in order to avoid the risk of corrosion, especially for metals and metal alloys (especially copper).

[0163] As mentioned above, the sulfur-containing fatty acid is preferably used in the aqueous lubricating composition according to the present invention in its neutralized form with an alkalizing agent, such as sodium hydroxide, potassium hydroxide or alkanolamines such as monoethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine and triisopropanolamine.

[0164] The aqueous lubricating composition according to the invention may contain 0.01% to 10% by mass, preferably 0.2% to 5% by mass, of antiwear and / or extreme pressure additives, in particular sulphur-containing fatty acids as defined above, relative to the total mass of the composition.

[0165] Defoaming agent

[0166] The aqueous lubricating composition according to the invention may contain at least one antifoaming agent additive.Antifoaming agents prevent the lubricating fluid from foaming.

[0167] It may for example be a defoamer based on polysiloxane or acrylate polymers.Preferably, the defoamer is selected from three-dimensional siloxanes.

[0168] Furthermore, the defoaming agent may be a polar polymer such as polymethylsiloxane or polyacrylate.

[0169] In particular, the aqueous lubricating composition according to the present invention may contain 0.001% to 3.0% by mass, preferably 0.005% to 1.5% by mass, more preferably 0.01% to 1.0% by mass of the defoamer additive relative to the total mass of the composition.

[0170] In a particular embodiment, the aqueous lubricating composition according to the invention comprises at least:

[0171] -water;

[0172] - at least one polyalkylene glycol;

[0173] - at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; trimerglycerol, and mixtures thereof;

[0174] - at least one gallic acid ester, in particular as defined above;

[0175] at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15, in particular as defined above, especially chosen from alkanolamines; and

[0176] - at least one antifoam additive, in particular chosen from three-dimensional silicones.

[0177] Metal passivator

[0178] The aqueous lubricating composition according to the present invention may contain at least one metal deactivator. Metal deactivators can protect metal parts by promoting the formation of metal oxides on their surfaces.

[0179] The metal deactivator may, for example, be selected from triazole derivatives, such as tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), amines substituted by triazole groups, such as N,N-bis(2-ethylhexyl)-1,2,4-triazol-1-ylmethylamine, N'-bis(2-ethylhexyl)-4-methyl-1H-benzotriazole-1-methylamine, N,N-bis(heptyl)-ar-methyl-1H-benzotriazole-1-methylamine, N,N-bis(nonyl)-ar-methyl-1H-benzotriazole-1-methylamine, N,N-bis(decyl)-ar-methyl-1H-benzotriazole-1-methylamine. Methyl-1H-benzotriazole-1-methylamine, N,N-bis(undecyl)-ar-methyl-1H-phenyltriazole-1-methylamine, N,N-bis(dodecyl)-ar-methyl-1H-benzotriazole-1-methylamine, N,N-bis(2-ethylhexyl)-ar-methyl-1H-benzotriazole-1-methylamine, 1,2,4-triazole, benzimidazole, 2-alkyldithiobenzimidazole, 2-alkyldithiobenzothiazole, 2-(N,N-dialkyldithiocarbamoyl)benzothiazole, 2,5-bis(alkyldithio)-1,3,4-thiadiazole , for example, 2,5-bis(tert-octyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-nonyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-decyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-undecyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-dodecyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-tridecyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-tetradecyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-pentadecyl disulfide)-1,3,4-thiadiazole 1,3,4-thiadiazole, 2,5-bis(tert-hexadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-heptadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-octadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-nonadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-eicosyldithio)-1,3,4-thiadiazole, 2,5-bis(N,N-dialkyldithiocarbamoyl)-1,3,4-thiadiazole, 2-alkyldithio-5-mercaptothiadiazole, and mixtures thereof.

[0180] Preferably, the metal deactivator is selected from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ) and salts thereof, employed individually or as a mixture.

[0181] The aqueous lubricating composition according to the present invention may particularly contain 0.01% to 2.0% by mass, preferably 0.1% to 1.0% by mass, more preferably 0.2% to 0.8% by mass of a metal deactivator relative to the total mass of the composition.

[0182] In a particular embodiment, the aqueous lubricating composition according to the invention comprises at least:

[0183] -water;

[0184] - at least one polyalkylene glycol;

[0185] - at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; trimerglycerol, and mixtures thereof;

[0186] - at least one gallic acid ester, in particular as defined above;

[0187] at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15, in particular as defined above, especially chosen from alkanolamines; and

[0188] - at least one metal deactivator, in particular chosen from triazole derivatives, more particularly chosen from tetrahydrobenzotriazole, tolyltriazole, benzotriazole and their salts, used alone or in the form of a mixture.

[0189] Colorants

[0190] The aqueous lubricating composition according to the invention may contain one or more colorants. The colorants may be natural or synthetic, typically organic.

[0191] The colorants that can be used in the aqueous lubricating composition can be more particularly chosen from natural or synthetic water-soluble colorants, such as the colorants FDC Red 4, DC Red 6, DC Red 22, DC Red 28, DC Red 30, DC Red 33, DC Orange 4, DC Yellow 5, DC Yellow 6, DC Yellow 8, FDC Green 3, DC Green 5, FDC Blue 1, betanin (beet), carmine, chlorophyllin, methylene blue, anthocyanins (anthocyanidins, black carrot and hibiscus), Tons, caramel, and riboflavin.

[0192] The aqueous lubricating composition according to the present invention may contain 0.01% to 2.0% by mass, preferably 0.01% to 1.5% by mass, more preferably 0.02% to 1.0% by mass of a colorant relative to the total mass of the composition.

[0193] In a particular embodiment, the aqueous lubricating composition according to the invention comprises at least:

[0194] -water;

[0195] - at least one polyalkylene glycol;

[0196] - at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; trimerglycerol, and mixtures thereof;

[0197] - at least one gallic acid ester, in particular as defined above;

[0198] at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15, in particular as defined above, especially chosen from alkanolamines; and

[0199] - at least one colorant, in particular chosen from ton,

[0200] Emulsifier

[0201] The aqueous lubricating composition according to the invention may contain one or more emulsifiers, also called emulsifying agents, which function to form a stable emulsion in water.

[0202] The emulsifier may more particularly be nonionic, for example ethoxylated fatty alcohols, ethoxylated fatty acids, ethoxylated fatty amides; anionic, for example soaps of KOH or NaOH; sulfonates; cationic, for example quaternary ammonium compounds; or water-soluble or water-emulsifiable carboxylates.

[0203] In particular, the aqueous lubricating composition according to the present invention may contain 0.01% to 10% by mass, preferably 0.1% to 5.0% by mass of an emulsifier relative to the total mass of the lubricating composition.

[0204] Chelating agents

[0205] The aqueous lubricating composition according to the invention may comprise at least one chelating agent. Chelating agents (also called sequestering agents) make it possible to limit scaling of metal ions in the composition.

[0206] As examples of chelating agents, mention may be made of those derived from phosphonic acids and phosphonates, such as diethylenetriaminepentamethylphosphonic acid (DTPMPA), aminotri(methylenephosphonic acid) (ATMP), hydroxyethanediphosphonic acid (HEDP), 1-hydroxyethylene 1,1-diphosphonate, 2-hydroxyethylaminedi(methylenephosphonic acid) (HEAMBP), diethylenetriaminopenta(methylenephosphonic acid) (DTMP), polyfunctional organic acids and hydroxy acids, such as ethylenediaminetetraacetic acid (EDTA), pteroyl-L-glutamic acid (PGLU), organic polyacids, such as maleic acid and polyaspartic acid, polysaccharides and carbohydrates, such as inulin, carboxymethylinulin and carboxymethylchitosan.

[0207] The aqueous lubricating composition according to the present invention may contain 0.001% to 2.0% by mass, preferably 0.01% to 1.0% by mass of a chelating agent relative to the total mass of the composition.

[0208] Biocides and Fungicides

[0209] The aqueous lubricating composition according to the invention may comprise at least one biocide and / or fungicide.Biocides and fungicides may be used to increase the biological stability of the composition by limiting the proliferation of bacteria, fungi and yeasts in the lubricating fluid.

[0210] Such biocides may be selected from parabens, aldehydes, reactive acetylacetonate compounds, isothiazolinones, phenolic compounds, acid salts, halogenated compounds, quaternary ammonium, certain alcohols, and mixtures thereof.

[0211] Preferably, the biocide may be selected from optionally substituted benzisothiazolinone (BIT), such as N-butyl-1,2-benzisothiazolin-3-one, methylisothiazolinone (MIT), a mixture of methylisothiazolinone and chloromethylisothiazolinone (MIT / CMIT), o-phenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate (IPBC), chlorocresol and N,N-methylenebismorpholine (MBM); sorbic acid; preferably selected from o-phenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate, chlorocresol, benzisothiazolinone and N,N-methylenebismorpholine.

[0212] The aqueous lubricating composition according to the invention may in particular comprise 0.01% to 10% by mass, preferably 0.5% to 5.0% by mass, of biocide and / or fungicide relative to the total mass of the composition.

[0213] According to a particular embodiment, the aqueous lubricating composition according to the invention comprises at least:

[0214] - water, in particular deionized water;

[0215] - at least one polyalkylene glycol, in particular as defined above;

[0216] - at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; preferably diethylene glycol;

[0217] - at least one gallic acid ester, in particular as defined above, especially lauryl gallate;

[0218] at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15, in particular as defined above, especially chosen from alkanolamines; and

[0219] - one or more other additives, selected from defoamers, corrosion inhibitors, metal deactivators, colorants, in particular as defined above.

[0220] In particular, the aqueous lubricating composition according to the present invention may comprise:

[0221] - at least 35% by weight of water, in particular deionized water;

[0222] - 5.0% to 50% by mass of at least one polyalkylene glycol, in particular as defined above;

[0223] -5.0% to 35% of at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; preferably diethylene glycol;

[0224] - 0.001% to 10% by mass of at least one gallic acid ester, in particular as defined above, especially lauryl gallate;

[0225] - 0.1% to 10% by mass of at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15, in particular as defined above, especially chosen from alkanolamines; and

[0226] - Optionally, 0.1% to 10% by mass of one or more other additives chosen from defoamers, corrosion inhibitors, metal deactivators, colorants, in particular as defined above.

[0227] More particularly, the aqueous lubricating composition according to the present invention may consist of:

[0228] - 5.0% to 50% by mass of at least one polyalkylene glycol, in particular as defined above;

[0229] -5.0% to 35% of at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; preferably diethylene glycol;

[0230] - 0.01% to 5% by mass of at least one gallic acid ester, in particular as defined above, especially lauryl gallate;

[0231] - 0.1% to 10% by mass of at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15, in particular as defined above, especially chosen from alkanolamines; and

[0232] - optionally, 0.1% to 10% by mass of one or more other additives, chosen from defoamers, corrosion inhibitors, metal deactivators, colorants, in particular as defined above,

[0233] The content is expressed relative to the total mass of the lubricating composition.

[0234] The balance consists of water, in particular deionized water.

[0235] It should be understood that the various specific embodiments described above can be combined as much as possible to define other specific embodiments.

[0236] In particular, each of the additives specifically described above may be introduced alone or in combination with at least one other of the additives specifically described, thereby defining different embodiment variants of the aqueous lubricating composition according to the invention.

[0237] In other words, a particular embodiment of the invention is defined by the aqueous lubricating composition according to the invention, which comprises at least water, one or more polyalkylene glycols; one or more antifreeze compounds, one or more gallic acid esters, in particular as defined above, one or more pH adjusting additives, in particular as defined above; preferably in the proportions as indicated above, and also one or more further additives specifically detailed herein.

[0238] Advantageously, the lubricating composition according to the invention has a kinematic viscosity (KV40), measured at 40° C. according to standard ASTM D445 (ISO 3104), of 10-1000 mm 2 / s, especially 20-300mm 2 / s, more particularly 25-80mm 2 / s.

[0239] The kinematic viscosity (KV100), measured at 100° C. according to standard ASTM D445 (ISO 3104), of the lubricating composition according to the invention may advantageously be between 3 and 50 mm 2 / s, especially 4-25mm 2 / s, especially 5-10mm 2 / s.

[0240] Advantageously, the lubricating composition according to the invention has a kinematic viscosity (KV-10) measured at -10°C according to standard ASTM D445 (ISO 3104) of 200-600 mm 2 / s, especially 250-500mm 2 / s, more particularly 275-400mm 2 / s.

[0241] application

[0242] As mentioned previously, in particular the aqueous lubricating composition formulated according to the present invention as described above has excellent tribological properties, in particular in terms of friction reduction and anti-wear properties, which makes it particularly suitable for use as a lubricating fluid.

[0243] The aqueous lubricating compositions can be used in a variety of applications. Typically, they can be used as lubricating fluids in systems and applications, replacing traditional hydrocarbon-based lubricants.

[0244] Therefore, the present invention is not limited to the specific application of the aqueous lubricant according to the present invention, and the following detailed discussion is given by way of illustration only and not limitation.

[0245] The mechanical parts lubricated with the lubricating composition according to the invention may be made of any material conventionally used in the relevant field, in particular metals such as steel, galvanized steel, stainless steel, yellow metals, but also ceramics or polymer materials.

[0246] It will be appreciated that the surfaces of these various materials may be coated, for example with a DLC (“Diamon Like Carbon”) coating.

[0247] As an illustration of conceivable applications, the aqueous lubricating composition according to the invention may be intended to lubricate moving parts in mechanical systems, and more particularly to lubricate mobile or stationary motorized systems.

[0248] Therefore, the aqueous lubricating composition according to the present invention can be used for lubricating and / or cooling a gear mechanism, a rolling bearing, a bearing (eg a rolling bearing or a sliding bearing) or an engine.

[0249] The term "motorization system" in the meaning of the present invention is understood to mean a system comprising all the mechanical components required for the intended mobile or stationary application and comprising at least one engine. It can be an internal combustion, gas (in particular hydrogen, ammonia), electric or hybrid motorization system, depending on the nature of the engine or engines included in the motorization system: internal combustion engine, gas (hydrogen, ammonia) engine and / or electric motor.

[0250] The term "stationary" motorized system within the meaning of the present invention is a motorized system comprising a stationary engine. It can be applied, for example, to a power plant. It can especially be a gas-fired motorized system, in particular a gas-fired stationary engine.

[0251] “Mobile” motorized systems are more particularly motorized systems used in vehicles, including light vehicles, heavy vehicles, so-called “off-road” mobile machines, or marine vehicles.

[0252] The mobile motorization system may thus be a propulsion system of a vehicle, in particular an electric or hybrid vehicle.

[0253] The term "propulsion system" in the meaning of the present invention refers to a system comprising the mechanical components necessary for propelling the vehicle. The propulsion system thus comprises more particularly an engine, an electric motor such as a rotor-stator assembly including power electronics (specifically for speed regulation), a transmission and optionally a battery. The battery itself is generally composed of a group of storage cells, also called cells.

[0254] The aqueous lubricating composition according to the invention advantageously enables fuel consumption to be effectively influenced by its influence on the friction forces generated between the various components of a motor vehicle. In particular, the aqueous lubricating composition proves to be particularly advantageous for reducing friction in gearboxes, in axle differentials and / or in cylinder heads.

[0255] By thus reducing the friction between the moving parts in the propulsion system of the vehicle, the lubricating composition according to the invention not only makes it possible to reduce wear but also to limit energy losses that lead to excessive fuel consumption.

[0256] The aqueous lubricating composition according to the invention therefore advantageously has good properties in terms of reducing the fuel consumption of motor vehicles (performance also known as “FuelEco”) and actually contributes to reducing CO 2 emissions.

[0257] The aqueous lubricating composition according to the invention can be used advantageously for the lubrication and / or cooling of the propulsion system of an electric or hybrid vehicle, and more particularly for lubricating the engine, power electronics, transmission and / or battery.

[0258] The aqueous composition according to the invention can be used both as a coolant and as a lubricant, for example in the propulsion system of an electric or hybrid vehicle. Advantageously, the composition according to the invention enables good performance to be achieved jointly in terms of cooling and lubrication of components of the propulsion system of an electric or hybrid vehicle, such as an electric motor of an electric or hybrid vehicle. It has proven to be particularly effective for cooling the rotor and / or stator of power electronics and / or electric motors. It also ensures the lubrication of rolling bearings located between the rotor and the stator of the electric motor of an electric or hybrid vehicle.

[0259] Furthermore, the composition according to the invention advantageously enables effective cooling of the batteries present in electric or hybrid vehicles.

[0260] Thus, advantageously, it is possible, for example, to ensure cooling of a battery and lubrication of a transmission, in particular a reduction gear, in an electric or hybrid vehicle by using a single composition according to the invention.

[0261] The aqueous lubricating composition according to the invention can be used as a running-in lubricant, for example for the running-in of mobile or stationary motorized systems.

[0262] In fact, a new or refurbished mechanical system may require proper lubrication when first started up to avoid initial damage to component surfaces until the mechanical system reaches its optimal operation.

[0263] As mentioned above, the aqueous lubricating composition according to the invention can also be used for applications as hydraulic fluids, in particular in hydraulic actuators (cylinders / motors) or machine components as required. In particular, hydraulic fluids are subject to continuous mechanical stress and high shear due to their continuous passage through the pump to maintain the appropriate pressure in the hydraulic system.

[0264] The aqueous lubricating composition according to the invention advantageously enables reduction of friction and wear under severe operating conditions, such as those encountered in hydraulic systems.

[0265] Therefore, the aqueous lubricating composition according to the present invention can be used to lubricate various moving parts in a hydraulic system. It can also ensure heat transfer between different components of the hydraulic system.

[0266] All the applications detailed above make it possible to illustrate certain advantageous embodiments of the aqueous lubricating composition according to the invention.

[0267] According to the invention, the properties, advantages or preferred features of the composition according to the invention make it possible to define the properties, advantages and preferred features of the use according to the invention. DETAILED DESCRIPTION Example

[0268] The invention will now be described by means of the following examples, which are given as non-limiting illustrations of the invention.

[0269] Evaluation of tribological properties

[0270] The tribological properties can be evaluated by testing on a rotating ball-on-disc (also called ball-on-plane) tribometer of the linear reciprocating tribometer type. This test makes it possible in particular to evaluate the performance of a lubricant in terms of friction in mixed / extreme operating conditions, depending on the applied load, pressure or speed conditions.

[0271] The coefficient of friction of the lubricating compositions tested was determined using a hardened steel ball having a diameter of approximately 2 cm (eg, 1.905 cm in diameter) at 40°C on a hardened steel flat surface.

[0272] The tribometer may be a device from Laboratoire de Tribologie Dynamique des Systèmes (LTDS). This device enables the relative movement of a steel ball and a steel plane in order to determine the coefficient of friction of a given lubricating composition while varying various properties such as speed, load and temperature. The hardened steel plane is a hardened steel plane with a mirror finish and the ball is also a ball made of hardened steel and is designated AISI 52100.

[0273] The applied load was 10 N and the rotational speed varied from 1 mm / s to 2500 mm / s. The friction coefficient was determined in particular at a rotational speed of 3 mm / s.

[0274] About 50 ml of the lubricating composition under test was introduced into the device. The ball was engaged against the flat surface, the ball and the flat surface being independently actuated to produce a mixed rolling / sliding contact.

[0275] The coefficient of friction is measured and recorded using a force sensor.

[0276] Solubilisation test

[0277] The solubilization of all ingredients in the lubricating composition was visually evaluated at the end of the formulation. If the composition was transparent, the solubilization was considered satisfactory. On the contrary, if the composition showed turbidity or precipitation, the solubilization was considered insufficient.

[0278] pH Measurement

[0279] At the end of formulation the pH of the composition was measured using a pH meter. Example 1

[0280] Preparation of lubricating composition

[0281] A reference aqueous lubricating composition not containing gallic acid esters was formulated by simply mixing at ambient temperature the following components in the percentages by mass indicated in the following Table 1. The percentages are therefore expressed in mass relative to the total mass of the composition.

[0282] The pH regulator is an alkanolamine such as dimethylethanolamine and makes it possible to maintain the pH of the composition between 8 and 15.

[0283] [Table 1]

[0284] (*) An additive mixture comprising one or more anti-corrosion additives, one or more passivating agents, one or more anti-foaming additives and / or one or more colorants.

[0285] Four aqueous lubricating compositions according to the invention (I1, I2, I3 and I4) were formulated by adding gallic acid esters to the reference composition at ambient temperature in the mass proportions detailed in Table 2 below.

[0286] [Table 2]

[0287] Four other aqueous lubricating compositions (I5, I6, I7 and I8) according to the present invention were formulated according to the following scheme.

[0288] Polyalkylene glycol and diethylene glycol were added to deionized water in the following proportions: deionized water 3 / 7, diethylene glycol 3 / 7 and polyalkylene glycol 1 / 7. The solution was stirred at a temperature of about 60° C. for 15 minutes in the presence of a magnetic stirrer.

[0289] The gallic acid ester was then added.

[0290] Finally, a pH adjusting additive (triethanolamine (TEA) or dimethylethanolamine (DMEA)) was added to the formulation.

[0291] The mass proportions of compositions I5 to I8 are detailed in Table 3 below.

[0292] [Table 3] Example 2

[0293] Characterization of composition

[0294] The coefficient of friction of the reference composition and the compositions according to the invention (I1, I2, I3 and I4) was determined. These results are given in Table 4 below.

[0295] [Table 4]

[0296] As can be seen from these examples, the compositions according to the invention (I1, I2, I3 and I4) have a significantly reduced coefficient of friction compared to the reference composition in which no gallic acid ester is used.

[0297] Therefore, the aqueous lubricating composition according to the invention has particularly advantageous properties in terms of friction reduction, in particular under severe lubrication conditions.

[0298] The compositions according to the invention (I5, I6, I7 and I8) are transparent, reflecting the good solubilization of the different ingredients they contain.

[0299] The aqueous lubricating compositions according to the invention therefore have a very good ability to dissolve the various compounds they contain, in particular antifreeze compounds, gallic acid esters and polyalkylene glycols.

Claims

1. An aqueous lubricating composition comprising at least: - water; - at least one polyalkylene glycol; - at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; trimerglycerol, and mixtures thereof; - at least one gallic acid ester; and - at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15.

2. The aqueous lubricating composition according to claim 1, characterized in that The water is permeate water, in particular deionized water.

3. The aqueous lubricating composition according to claim 1 or 2, comprising at least 20% by mass, preferably at least 30% by mass, especially 35% to 90% by mass, more preferably 40% to 75% by mass of water, especially deionized water, relative to the total mass of the composition.

4. The aqueous lubricating composition according to any one of the preceding claims, characterized in that The one or more pH adjusting additives are chosen from alkanolamines, in particular ethanolamines, and more particularly from dimethylethanolamine, triethanolamine, and mixtures thereof, more particularly dimethylethanolamine.

5. The aqueous lubricating composition according to any one of the preceding claims, characterized in that The content of the one or more pH adjusting additives is 0.1% to 10% by mass, preferably 0.5% to 5% by mass, relative to the total mass of the composition.

6. The aqueous lubricating composition according to any one of the preceding claims, characterized in that The one or more polyalkylene glycols contain at least 50% by mass, in particular at least 80% by mass, more preferably at least 90% by mass of propylene oxide and / or ethylene oxide units, in particular the one or more polyalkylene glycols are ethylene oxide / propylene oxide copolymers.

7. The aqueous lubricating composition according to any one of the preceding claims, characterized in that The one or more polyalkylene glycols have a kinematic viscosity (KV100) measured at 100° C. according to ASTM D445 standard between 100 and 25000 mm 2 / s, especially between 150 and 10 000 mm 2 / s.

8. The aqueous lubricating composition according to any one of the preceding claims, comprising at least 5.0% by mass, preferably 5.0% to 50% by mass, more preferably 10% to 40% by mass, in particular 10% to 20% by mass of one or more polyalkylene glycols, relative to the total mass of the composition.

9. An aqueous lubricating composition according to any one of the preceding claims, characterized in that The antifreeze compound is selected from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof, in particular diethylene glycol.

10. The aqueous lubricating composition according to any one of the preceding claims, comprising at least 5.0% by mass, preferably 5.0% to 45% by mass, more preferably 10% to 35% by mass, in particular 20% to 35% by mass of one or more antifreeze compounds relative to the total mass of the composition.

11. An aqueous lubricating composition according to any one of the preceding claims, characterized in that The gallic acid ester is obtained from a monohydric alcohol comprising 1 to 24 carbon atoms, preferably 3 to 20 carbon atoms, in particular 3 to 18 carbon atoms, more preferably 6 to 16 carbon atoms, for example 8 to 14 carbon atoms, in particular selected from 1-octanol and 1-dodecanol.

12. An aqueous lubricating composition according to any one of the preceding claims, characterized in that The gallic acid ester has the following formula (I): wherein R represents a saturated, mono- or polyunsaturated, linear or branched hydrocarbon chain, preferably a linear and saturated hydrocarbon chain, having C1-C 24 , preferably C3-C 20 , more preferably C3-C 18 , especially C6-C 16 , such as C8-C 14 , preferably, the gallic acid ester is lauryl gallate.

13. The aqueous lubricating composition according to any one of the preceding claims, comprising 0.001-10% by mass, in particular 0.01-5% by mass, more particularly 0.1-2% by mass of one or more gallic acid esters relative to the total mass of the composition.

14. The aqueous lubricating composition according to any one of the preceding claims, further comprising at least one additive selected from the group consisting of defoamers, biocides, corrosion inhibitors, antiwear and / or extreme pressure additives, chelating agents, metal passivators, colorants, dispersants, emulsifiers and mixtures thereof, preferably selected from the group consisting of defoamers, corrosion inhibitors, metal passivators, colorants and mixtures thereof.

15. Aqueous lubricating composition according to any one of the preceding claims, comprising less than 5% by mass, preferably less than 2% by mass, more preferably less than 1% by mass of water-insoluble oil relative to the total mass of the composition, the composition more particularly being free of water-insoluble oil.

16. Use of an aqueous lubricating composition as defined in any of the preceding claims for lubricating and / or cooling moving parts in mechanical systems, for example for lubricating and / or cooling mobile or stationary motorized systems or as a hydraulic fluid.

17. Use of at least one gallic acid ester, in particular a gallic acid ester as defined in claim 11 or 12, as an additive for improving the tribological properties, in particular with regard to friction reduction, of an aqueous composition which also comprises at least: water, at least one polyalkylene glycol and at least one antifreeze compound selected from glycols and at least one pH regulating additive which maintains the pH of the composition between 8 and 15.

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