Use of polyalkylene glycols as antifreeze agents in an aqueous lubricating composition

Abstract

Use of Polyalkylene Glycols as Antifreeze Agents in an Aqueous Lubricating Composition. The present invention relates to the use of at least one polyalkylene glycol, denoted PAG, with a weight-average molecular weight, Mw, of at least 1500 g / mol, as an antifreeze agent in an aqueous lubricating composition. It also relates to an aqueous lubricating composition comprising at least: - water, in particular deionized water; - at least 10% by mass, relative to the total mass of said composition, of one or more polyalkylene glycols with a weight-average molecular weight, Mw, of at least 1500 g / mol, said aqueous lubricating composition comprising an additional antifreeze compound content strictly less than 1% by mass, relative to the total mass of said composition. Figure for the abstract: None

Description

Title of the invention: Use of polyalkylene glycols as antifreeze agents in an aqueous lubricating composition Technical field

[0001] The present invention relates to the field of lubricating compositions, and more particularly to aqueous-based lubricating compositions. These lubricating compositions can be used for various applications, in particular as hydraulic fluids, for the lubrication and / or cooling of various mechanical systems, such as bearings, gears, bearings or engines.

[0002] More particularly, the present invention proposes the formulation of new aqueous lubricating compositions in which the polyalkylene glycols are notably used as antifreeze agents. Prior art

[0003] Lubricating compositions, also called "lubricants", are commonly used in mechanical systems to reduce friction between parts and thus protect the parts against wear. In addition to wear phenomena, friction can oppose the relative movement of the parts in contact and induce energy losses that are detrimental to optimal operation of the mechanical system.

[0004] Lubricants are used for multiple applications, for example for metalworking, in particular for metal deformation operations, for gas or steam turbines in the fields of aeronautics, naval, rail transport and electricity production, for propulsion systems of motor vehicles, for example for the lubrication of bearings, gears, an engine, etc.

[0005] For example, in the field of lubricants for motor vehicle engines or transmissions, the formulation of lubricants represents an important issue insofar as they make it possible to act on fuel consumption, and consequently on carbon dioxide emissions, via their impact on the friction forces generated between the different components of motor vehicles.

[0006] The most widespread lubricants are hydrocarbon-based lubricants. These hydrocarbon lubricants are conventionally composed of one or more base oils, to which are generally associated additives dedicated to boosting the lubricating performance of the base oils, for example friction modifying additives.

[0007] On the other hand, friction between moving parts generates heat, and it can It may be necessary to jointly provide cooling for mechanical systems. This cooling is typically provided by a cooling fluid, separate from the hydrocarbon lubricant, such as air, an aqueous fluid, such as water, or a mixture of water and a glycol.

[0008] Nowadays, the development of new lubricants must take into consideration new constraints aimed at reducing, or even eliminating, the use of toxic or potentially toxic solvents, or at reducing their impact on the environment and carbon dioxide emissions. In this respect, water-based formulations are of increasing interest.

[0009] Although water is an excellent cooling fluid, it does not, however, have the tribological properties required for a lubricant, particularly in terms of reducing friction and protecting parts against wear or cold properties. Additive systems are therefore implemented.

[0010] In particular, to prevent freezing of the water-based lubricant during use or storage under low temperature conditions, an antifreeze additive, typically a glycol such as ethylene glycol, propylene glycol or diethylene glycol, or glycerol, is added to the lubricant, for the purpose of reducing the pour point of the lubricant.

[0011] By way of example, document US 2012 / 0149616 proposes an aqueous lubricant comprising, in addition to water, water-soluble polyalkylene glycols, emulsifiers, antifreeze additives of alkylene glycol or glycerol type, anticorrosion additives, antifoam additives and friction reducing additives.

[0012] Application WO 2021 / 259853 also describes an aqueous lubricating composition, combining a polyalkylene glycol, an antifreeze compound such as monoethylene glycol, and a phosphorus compound.

[0013] The glycols proposed as antifreeze additives, the least expensive and most widespread, ethylene glycol and diethylene glycol, nevertheless present a certain toxicity. They also contribute in an undesirable way to increasing the environmental footprint of the lubricant, in particular to the emission of greenhouse gases.

[0014] Therefore, it would be desirable to be able to reduce, or even eliminate, the presence of these glycols used as antifreeze additives, in order to further reduce the environmental footprint of aqueous lubricants, without however affecting the cold properties of aqueous lubricants.

[0015] The present invention aims precisely to meet this expectation. Statement of the invention

[0016] The invention thus relates, according to a first of its aspects, to the use of at least one polyalkylene glycol, of weight-average molecular mass, Mw, of at least 1500 g / mol, as an antifreeze agent in an aqueous lubricating composition.

[0017] Unexpectedly, the inventors have thus found that polyalkylene glycols, typically used as thickening agents in the formulation of aqueous lubricants, are capable of providing the aqueous lubricant with antifreeze properties.

[0018] For the purposes of the invention, the term "antifreeze agent or additive" means a compound making it possible to provide antifreeze properties, i.e. to lower the pour point of the composition in which it is used, in the present case, the aqueous lubricating composition.

[0019] The antifreeze properties can be assessed by measuring the change in the pour point when the antifreeze compound is added to a water-based formulation, for example in water. The pour point, corresponding to the temperature below which the formulation begins to solidify, can for example be measured according to ASTM D97 or ISO 3016.

[0020] The addition of a so-called "antifreeze" compound thus makes it possible to lower the pour point of the lubricant. The antifreeze properties of the lubricant ensure that the lubricant has good cold properties. For example, the lubricant used in a motorization system must be sufficiently fluid when the engine is started (when cold) to lubricate the mechanical parts. The pour point value that a lubricant must satisfy naturally varies depending on the type of lubricant (hydraulic, reducer, engine, etc.) and the intended application (more or less cold conditions). As an illustration, the recommended pour point value for a standard (mineral) hydraulic oil is -15°C / -12°C; for an "off-road" (mineral) hydraulic oil with improved temperature properties (viscosity index and pour point in particular) is -27°C / -24°C, for a standard (mineral) oil for reducers it is -9°C.

[0021] Preferably, said polyalkylene glycol(s) are used in an amount of at least 10% by mass, in particular at least 15% by mass and more particularly from 15% to 50% by mass, relative to the total mass of the aqueous lubricating composition.

[0022] Advantageously, it is thus possible according to the invention to avoid the use of glycol-type antifreeze additives, such as monoethylene glycol, diethylene glycol, monopropylene glycol, or even any other additives proposed until now as antifreeze agents in aqueous lubricant formulas, such as glycerol.

[0023] The aqueous lubricating composition in which said polyalkylene glycol(s) are used according to the invention can thus advantageously comprise a content of glycol-type antifreeze additive(s), for example monoethylene glycol, diethylene glycol, and / or monopropylene glycol, and / or glycerol, strictly lower at 5% by mass relative to the total mass of said aqueous lubricating composition, in particular strictly less than 1% by mass, preferably less than or equal to 0.5% by mass, or even be completely free of such antifreeze additives.

[0024] More generally, an aqueous lubricating composition in which said polyalkylene glycol(s) are used according to the invention may comprise a content of additional antifreeze additive(s), in particular chosen from glycols, in particular alkylene glycols having from 2 to 6 carbon atoms such as monoethylene glycol and / or monopropylene glycol and oxyalkylene glycols having from 4 to 14 carbon atoms such as diethylene glycol; aliphatic monoethers of said glycol and polyhydric aliphatic alcohols such as glycerol, strictly less than 5% by mass relative to the total mass of said aqueous lubricating composition, in particular strictly less than 1% by mass, preferably less than or equal to 0.5% by mass, in particular less than or equal to 0.1% by mass or even be totally free of such antifreeze additives.

[0025] Furthermore, said polyalkylene glycol(s) fulfill the dual function of thickening agent and antifreeze agent, without significantly increasing the concentrations generally used when polyalkylene glycols are introduced as thickening agents, which advantageously makes it possible to reduce the quantity of additives required for the formulation of the aqueous lubricant.

[0026] An aqueous lubricating composition according to the invention has the advantage of being easy to formulate.

[0027] Advantageously, the invention makes it possible, by reducing the quantity, or even by eliminating the glycol-type antifreeze additives commonly used in aqueous lubricants, to reduce the toxicity and environmental footprint of the lubricants, in particular their impact on carbon dioxide emissions, while retaining good cold properties.

[0028] The environmental footprint associated with the production of a lubricant can be evaluated, as illustrated in the examples which follow, according to different indicators defined by the European Union, including in particular the “climate change” indicator which is a data item of the global warming potential associated with the emission of greenhouse gases, expressed in equivalent kilograms of carbon dioxide (kg CO2 eq).

[0029] The use of said polyalkylene glycol(s) according to the invention can be implemented to improve the climate change indicator of said aqueous lubricating composition. This indicator is detailed in particular in the “Example 2” section below.

[0030] According to a particularly preferred embodiment, as detailed in the remainder of the text, all or part of said polyalkylene glycol(s) used according to the invention are bio-sourced (not of fossil origin), which further reduces the environmental footprint of the aqueous lubricants proposed according to the invention, in particular their impact on greenhouse gas emissions.

[0031] The invention also relates, according to another of its aspects, to an aqueous lubricating composition comprising at least: - water, especially deionized water;

[0032] - at least 10% by mass, relative to the total mass of said composition, of a or more polyalkylene glycol(s) with a weight-average molecular mass, Mw, of at least 1500 g.mol *,

[0033] said aqueous lubricating composition comprising a content of additional antifreeze compound(s), in particular chosen from glycols, in particular alkylene glycols having from 2 to 6 carbon atoms such as monoethylene glycol and / or monopropylene glycol and oxyalkylene glycols having from 4 to 14 carbon atoms such as diethylene glycol; aliphatic monoethers of said glycols and polyhydric aliphatic alcohols such as glycerol, strictly less than 1% by mass, relative to the total mass of said composition.

[0034] Preferably, said polyalkylene glycol(s) are present in a content of at least 15% by mass relative to the total mass of said aqueous lubricating composition.

[0035] Preferably, said polyalkylene glycol(s) (PAG(s)) are present in the aqueous lubricating composition in a PAG(s) / water mass ratio of less than or equal to 0.30, in particular less than or equal to 0.25 and more particularly less than or equal to 0.20.

[0036] Preferably, the water content, in particular deionized water, of an aqueous lubricating composition according to the invention is greater than or equal to 15% by mass, in particular greater than or equal to 30% by mass.

[0037] A lubricating composition according to the invention advantageously has excellent cooling and fire resistance properties.

[0038] The lubricating compositions according to the invention, having good cold properties, can be used over a wide range of temperatures, in particular from -20°C to +70°C.

[0039] They can thus be implemented for multiple applications, in particular as hydraulic fluids or for the lubrication and / or cooling of various mechanical systems. They can thus be used in all systems and for all applications, as a substitute for conventionally used lubricants, in particular hydrocarbon lubricants. Examples of application are given in the rest of the text.

[0040] Thus, the invention also relates to the use of an aqueous lubricating composition according to the invention, for the lubrication and / or cooling of moving parts in a mechanical system, for example for the lubrication and / or cooling of mobile or stationary drive systems, or as a hydraulic fluid, in particular at a temperature between -20°C and +70°C.

[0041] The invention also relates to a method for lubricating a mechanical system, in particular in a mobile or stationary motorization system, comprising a step of bringing at least one part of said mechanical system into contact with an aqueous lubricating composition according to the invention.

[0042] The present invention also relates to the use of an aqueous lubricating composition according to the invention, for reducing friction between moving parts in a mechanical system, as well as the use of an aqueous lubricating composition according to the invention for reducing wear of parts in a mechanical system.

[0043] Advantageously, a composition according to the invention combines good tribological properties, in particular friction reduction and / or wear resistance, more particularly friction reduction, and good cooling properties linked to the presence of water. Thus, an aqueous composition according to the invention can advantageously ensure the dual function of lubrication and cooling.

[0044] It is thus possible to take advantage of an aqueous lubricating composition according to the invention to avoid the use of two separate fluids, on the one hand a cooling fluid, on the other, a lubricating fluid.

[0045] Other characteristics, variants and advantages of the use of polyalkylene glycols as antifreeze agents, and of the aqueous lubricating compositions formulated according to the invention, will become more apparent on reading the description and examples which follow, given by way of illustration and not limitation of the invention.

[0046] The expressions “between ... and ...”, “ranging from ... to ...”, “formed from ... to ...”, and “varying from ... to ...”, must be understood inclusively, unless otherwise stated.

[0047] In the description and examples, unless otherwise indicated, the percentages are weight percentages. The percentages are therefore expressed by mass relative to the total mass of the composition. The temperature is expressed in degrees Celsius unless otherwise indicated, and the pressure is atmospheric pressure, unless otherwise indicated. Brief description of the drawings

[0048] [Fig-1] represents the results of the environmental footprint assessment, according to different indicators, associated with a CCI reference lubricant using diethylene glycol as an antifreeze additive, and with the lubricants according to the invention CL1 and CL2, described in example 2. Detailed description AQUEOUS LUBRICANT COMPOSITION

[0049] As indicated previously, the invention is based on the use, as an antifreeze agent, of one or more polyalkylene glycols for the formulation of an aqueous lubricating composition.

[0050] For the purposes of the invention, an aqueous lubricating composition, also called an aqueous lubricant, is a formulation comprising water. In particular, water is present as the majority solvent, in other words in a greater quantity than any other solvent possibly present in the composition.

[0051] Preferably, an aqueous lubricating composition comprises at least 15% by mass of water, in particular demineralized water, for example deionized water, preferably at least 30% by mass, more particularly from 30% to 85% by mass.

[0052] Advantageously, in addition to its role as a solvent, water provides access to a lubricating composition having good cooling properties, and which can be used as a cooling fluid for moving parts in a mechanical system.

[0053] According to a particular embodiment, the water used in an aqueous lubricating composition formulated according to the invention is osmosed or demineralized water, more preferably deionized water.

[0054] For the purposes of the present invention, the term “osmosed water” is intended to denote water that has undergone purification, in particular by a reverse osmosis process, in order to reduce the content of organic and / or mineral compounds, for example to a content of less than 5.0% by weight, preferably less than 1.0% by weight. In the remainder of the text, the expressions “demineralized water” or “ultrapure water” will be considered equivalent or synonymous with the expression “osmosed water”. In particular, osmosed water may be “deionized water”, in other words water that has undergone purification in order to reduce the content of ions, such as the Ca2+ and HCO3 ions generally present in water. Preferably, deionized water does not comprise ions.

[0055] The use of deionized water is therefore particularly advantageous in the context of the use of the aqueous lubricant according to the invention for applications requiring a fluid that conducts little, or even not at all, electricity, such as for example for the use of the aqueous lubricant for the lubrication and cooling of mechanical systems comprising an electrical circuit, for example electric or hybrid motors, in particular in electric or hybrid vehicles.

[0056] An aqueous lubricating composition according to the invention therefore differs from lu oil-based lubricants conventionally used in mechanical systems, which comprise a majority proportion of one or more base oils that are not soluble in water.

[0057] By "water-insoluble oil" is meant in particular an oil which does not dissolve substantially in water at room temperature (about 25°C). In particular, a water-insoluble oil has a solubility in water of less than 0.2 g / L, at room temperature.

[0058] These include lubricating base oils belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and their mixtures.

[0059] Preferably, an aqueous lubricating composition according to the present invention comprises less than 5% by mass of oil(s) not soluble in water, preferably less than 2% by mass, more preferably less than 1% by mass, relative to the total mass of the composition.

[0060] Advantageously, an aqueous lubricating composition according to the invention is completely free of oil which is not soluble in water. Polyalkylene glycol

[0061] As previously indicated, an aqueous lubricating composition comprises one or more polyalkylene glycols as an antifreeze agent.

[0062] The polyalkylene glycols (denoted “PAG”) are more particularly chosen from water-soluble or water-soluble polyalkylene glycols.

[0063] By "water soluble" is meant a polyalkylene glycol having a water solubility of at least 10 g / L, preferably at least 500 g / L, in water at room temperature (about 25°C).

[0064] Preferably, said polyalkylene glycol(s) used according to the invention are chosen from polyalkylene glycols having a cloud point (called “Cloud point” in English), in other words having the property of inverse demixing (or “inverse solubility” in English).

[0065] The reverse demixing property characterizes the property of certain polyalkylene glycols to be soluble in water up to a temperature beyond which they become insoluble. This turbidity or "cloudiness" indicates phase separation with water, which results in a deposition of said polyalkylene glycol on the surfaces in contact with the lubricant.

[0066] The temperature at which turbidity and insolubility occur is called the cloud point of the polyalkylene glycol. The cloud point can be determined, for example, according to ASTM D 2024 or DIN EN 1890, generally for a mixture of 1% by mass of polyalkylene glycol in water.

[0067] Preferably, the said polyalkylene glycol(s) used according to the invention have a cloud point greater than or equal to 70°C.

[0068] The water solubility and reverse demixing properties of the said polyalkylene glycol(s) used according to the invention advantageously make it possible to increase the lubrication properties.

[0069] Advantageously, a polyalkylene glycol used according to the invention comprises at least 50% by mass, in particular at least 80% by mass, more preferably at least 90% by mass, or even at least 95% by mass of propylene oxide and / or ethylene oxide units. In particular, the polyalkylene glycols used according to the invention consist of propylene oxide and / or ethylene oxide units.

[0070] Preferably, the polyalkylene glycol used according to the invention may be a copolymer, in particular a random copolymer, of ethylene oxide (EO) and propylene oxide (PO). In particular, the ethylene oxide (EO) and propylene oxide (PO) units are present in the copolymer in an EO / PO mass ratio of between 50 / 50 and 90 / 10, in particular between 60 / 40 and 85 / 15, and more particularly between 70 / 30 and 80 / 20.

[0071] Preferably, the polyalkylene glycol used according to the invention is obtained by polymerization from one or more alkylene oxide monomers, in particular ethylene oxide and / or propylene oxide, initiated by a compound of alcohol type, in particular of polyol type, preferably by a diol compound.

[0072] In particular, the polyalkylene glycol used according to the invention comprises hydroxyl terminal functions. By "terminal functions", within the meaning of the invention, is meant the functions located at the ends of the polymer chains.

[0073] As indicated previously, the said polyalkylene glycol(s) used according to the invention have a weight-average molecular mass (Mw) greater than or equal to 1500 g / mol.

[0074] In particular, a polyalkylene glycol is distinguished from alkylene glycol oligomers having a number of monomeric units less than or equal to ten.

[0075] Preferably, a polyalkylene glycol used according to the invention has a weight-average molecular mass (Mw) of at least 2000 g.mol ', in particular at least 2500 g.mol *, more particularly at least 3000 g.mol *, in particular between 3000 and 50,000 g.mol *, or even between 5000 and 25,000 g.mol *, preferably between 5,000 and 15,000 g.mol *.

[0076] Weight average molecular weight can be measured by gel permeation chromatography (GPC).

[0077] Preferably, a polyalkylene glycol used according to the invention has a kinematic viscosity measured at 100°C (KV100), according to standard ASTM D445, of between 100 and 25,000 mm2 / s, in particular between 150 and 15,000 mm2 / s.

[0078] Preferably, a polyalkylene glycol used according to the invention has a kinematic viscosity measured at 40°C (KV40), according to ASTM D445, between 500 and 100,000 mm2 / s, more particularly between 1,000 and 70,000 mm2 / s.

[0079] The flash point of a polyalkylene glycol used according to the invention is preferably greater than or equal to 160°C, in particular greater than or equal to 220°C. The flash point can be measured by the ISO 2592 or ASTM D92 standard.

[0080] Preferably, a polyalkylene glycol used according to the invention has a viscosity index measured according to the ASTM D2270 standard, between 100 and 800, preferably between 250 and 550.

[0081] It is understood that a single polyalkylene glycol or a mixture of several different polyalkylene glycols, in particular as described above, can be used according to the invention.

[0082] In particular, an aqueous lubricating composition according to the invention may comprise a mixture of at least two distinct polyalkylene glycols, more particularly at least one polyalkylene glycol of low weight average molecular mass and at least one polyalkylene glycol of high weight average molecular mass.

[0083] It is within the general skills of a person skilled in the art to adjust the nature and content of low and high weight-average molecular weight polyalkylene glycols in the polyalkylene glycol mixture, particularly with regard to the viscosity targeted for the final lubricating composition.

[0084] According to a particularly advantageous embodiment, said polyalkylene glycol(s) used according to the invention are biosourced.

[0085] For the purposes of the invention, a “bio-sourced” compound means a compound derived, partially or totally, from biomass, or obtained from renewable raw materials derived from biomass, in particular from plants.

[0086] Advantageously, the implementation according to the invention of one or more biosourced PAGs thus makes it possible to further reduce the carbon footprint of the lubricating composition according to the invention.

[0087] Preferably, said polyalkylene glycol(s) are used in an amount of at least 10% by mass relative to the total mass of the aqueous lubricating composition, preferably at least 15% by mass, in particular from 15% to 50% by mass, more particularly from 15% to 30% by mass, or even from 16% to 20% by mass, relative to the total mass of the aqueous lubricating composition.

[0088] In a particular embodiment, said polyalkylene glycol(s) are present in an aqueous lubricating composition according to the invention in a PAG(s) / water mass ratio less than or equal to 0.30, in particular between 0.10 and 0.30, more particularly between 0.15 and 0.25, and in particular between 0.15 and 0.20.

[0089] According to a particular embodiment, the assembly consisting of water and the or said polyalkylene glycol(s) represent more than 80% of the total mass of said aqueous lubricating composition. Antifreeze additive annex

[0090] As indicated previously, an aqueous lubricating composition according to the invention advantageously comprises a reduced content of antifreeze additives previously proposed in aqueous lubricants, also called antifreeze compounds.

[0091] The “conventional” antifreeze additives, proposed for aqueous lubricants, are molecules or oligomers having a number of monomeric units strictly less than ten, and therefore distinct from the polyalkylene glycols considered according to the invention.

[0092] In particular, the antifreeze additives may be chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols.

[0093] Glycols are diols in which the two hydroxyl groups are carried by different carbon atoms, preferably by vicinal carbon atoms. Glycol-type antifreeze additives are more particularly alkylene glycols having from 2 to 6, preferably from 2 to 4, carbon atoms, such as monoethylene glycol, monopropylene glycol and monobutylene glycol, and oxyalkylene glycols, preferably oxyethylene and oxypropylene glycols, having from 4 to 14 carbon atoms, preferably from 4 to 10 carbon atoms, such as diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol and tripropylene glycol.

[0094] Preferably, the content of glycol-type antifreeze compound(s), for example monoethylene glycol, diethylene glycol, and / or monopropylene glycol, if present in an aqueous lubricating composition according to the invention, is strictly less than 5% by mass, in particular strictly less than 1% by mass, preferably less than or equal to 0.5% by mass, in particular less than or equal to 0.1% by mass, relative to the total mass of the composition.

[0095] Advantageously, an aqueous lubricating composition according to the invention is completely free of glycol-type antifreeze compound, and thus makes it possible to overcome the toxicity effects associated with these compounds. An aqueous lubricating composition according to the invention thus advantageously has reduced toxicity.

[0096] Known antifreeze additives for aqueous lubricants may also be aliphatic monoethers of glycols as mentioned above, for example monomethyl, monoethyl, monopropyl and monobutyl ethers.

[0097] It may also be polyhydric aliphatic alcohols, in particular glycerol, diglycerol, triglycerol, erythritol and pentaerythritol.

[0098] Preferably, the content of additional antifreeze additive(s), in particular chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, in particular as described above, if present in a composition aqueous lubricating position according to the invention, is strictly less than 5% by mass.

[0099] Thus, an aqueous lubricating composition according to the invention differs from the aqueous lubricants proposed until now which comprise an effective quantity (in other words a quantity sufficient to provide the required antifreeze properties) of one or more antifreeze additives chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, in particular as described above.

[0100] In particular, an aqueous lubricating composition as claimed according to the invention comprises a content of additional antifreeze additives, in particular chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% by mass, in particular less than or equal to 0.5% by mass and more particularly less than or equal to 0.1% by mass.

[0101] Preferably, an aqueous lubricating composition as claimed according to the invention is free from additional antifreeze additives other than said PAG(s) used according to the invention.

[0102] In a particular embodiment, an aqueous lubricating composition according to the invention comprises at least:

[0103] - at least 15% by mass, in particular at least 30% by mass and more particu mainly from 30% to 85% by mass of water, preferably deionized water;

[0104] - at least 15% by mass, in particular from 15% to 50% by mass, more particu 15% to 30% by mass of one or more polyalkylene glycol(s) (PAG(s)) with a weight-average molecular mass, Mw, of at least 1500 g.mol1;

[0105] the PAG(s) / water mass ratio being less than or equal to 0.30, in particular between 0.10 and 0.30, more particularly between 0.15 and 0.25, and in particular between 0.15 and 0.20;

[0106] said aqueous lubricating composition comprising a content of additional antifreeze compound(s), in particular chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% by mass, preferably less than or equal to 0.5% by mass, or even less than or equal to 0.1% by mass; the contents being indicated in relation to the total mass of said lubricating composition. Other additives

[0107] An aqueous lubricating composition according to the invention may further comprise various other additives.

[0108] It is understood that the said additive(s) are compatible with their implementation in aqueous medium. Advantageously, the additives are implemented in a form that is soluble or emulsifiable in water, for example in the form of salts or ionic liquids.

[0109] The said additive(s) are of course chosen with regard to the intended application for the aqueous lubricant.

[0110] A person skilled in the art will take care to choose the possible additives and / or their quantity in such a way that the advantageous properties of the aqueous lubricating composition used according to the invention, in particular the antifreeze properties, are not impaired by the envisaged addition.

[0111] Such additives may be more particularly chosen from antifoam agents, biocides, pH regulators, corrosion inhibitors, anti-wear and / or extreme pressure additives, sequestering agents, metal passivating agents, colorants, dispersants, emulsifying agents, and mixtures thereof.

[0112] Advantageously, an aqueous lubricating composition according to the invention may comprise one or more additives chosen from anti-foam agents, extreme pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, colorants, and mixtures thereof.

[0113] An aqueous lubricating composition according to the invention may more particularly comprise from 0.1 to 10% by mass of additives, in particular from 1.0 to 8.0% by mass of additives, in particular from 1.0 to 5.0% by mass, relative to the total mass of the composition. pH regulator

[0114] An aqueous lubricating composition according to the invention may comprise at least one pH regulating additive, in particular an alkaline buffer. The pH regulator advantageously makes it possible to maintain the desired pH of the lubricating composition, in particular in order to preserve an alkaline pH, advantageously between 8 and 15.

[0115] Said pH regulator(s), by ensuring that the pH of the aqueous lubricating composition is maintained between 8 and 15, makes it possible in particular to prevent corrosion of the metal surfaces, but also to promote the solubilization of the various compounds in the lubricating composition, in particular of the polyalkylene glycol(s), in particular as defined above.

[0116] The pH regulator can be chosen from the family of amines, in particular alkanolamines and amino alcohols.

[0117] It may in particular be a pH regulating additive chosen from 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); ethylene amines, such as ethylene diamine (EDA), diethylene triamine (DETA), triethylene tetramine (TETA), and tetraethylene pentamine (TEPA); cyclamines, such as cyclohexylamine; 2-amino-2-ethyl-1,3-propanediol; 2-amino-2-methyl-1-propanol; and mixtures thereof.

[0118] An aqueous lubricating composition according to the invention may in particular comprise from 0.1% to 10% by mass of pH regulating additive(s), preferably from 0.5% to 5% by mass, relative to the total mass of the composition.

[0119] Advantageously, an aqueous lubricating composition according to the invention comprises at least one pH regulating additive making it possible to maintain the pH of said lubricating composition between 8 and 15, in particular between 8.5 and 14, more particularly between 9 and 13, said pH regulating additive being chosen in particular from alkanolamines, preferably ethanolamines, and more particularly from dimethylethanolamine (DMEA), triethanolamine (TEA), diglycolamine (DGA) and mixtures thereof.

[0120] In a particular embodiment, an aqueous lubricating composition according to the invention comprises at least: - water, especially deionized water; - at least 10% by mass, in particular at least 15% by mass, of one or more polyalkylene glycol(s) with a weight-average molecular mass, Mw, of at least 1500 g / mol;

[0121] - at least one pH regulating additive making it possible to maintain the pH of said com lubricating position between 8 and 15, in particular chosen from alkanolamines and diglycolamine; said aqueous lubricating composition comprising a content of additional antifreeze compound(s), in particular chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% by mass, preferably less than or equal to 0.5% by mass, or even less than or equal to 0.1% by mass;

[0122] the contents being expressed relative to the total mass of the composition. Corrosion inhibitor

[0123] An aqueous lubricating composition according to the invention may comprise at least one corrosion inhibiting agent. Corrosion inhibitors advantageously make it possible to reduce or even prevent corrosion of metal parts. The nature of said corrosion inhibitor(s) may be chosen with regard to the metal to be protected against corrosion, such as aluminum, steel, galvanized steel, yellow metals, for example copper or brass.

[0124] Among the inorganic corrosion inhibitors that may be mentioned are nitrites, sulfites, silicates, borates, sodium, potassium, calcium or phosphates. magnesium, alkali metal phosphates, hydroxides, molybdates, zinc, magnesium or nickel sulfates.

[0125] Among the organic corrosion inhibitors that may be mentioned are alkanolamines, such as triethanolamine, aliphatic monocarboxylic acids, in particular having from 4 to 15 carbon atoms, for example octanoic acid, aliphatic dicarboxylic acids having from 4 to 15 carbon atoms, for example decanedioic acid, undecanedioic acid, dodecanedioic acid or mixtures thereof, polycarboxylic acids optionally neutralized by triethanolamine, such as 1,3,5-triazine-2,4,6-tri-(6-aminocaproic) acid, alkanoyl-laminidocarboxylic acids, in particular isononanoylamidocaproic acid, and mixtures thereof. Borated amides, products of the reaction of amines or amino alcohols with boric acid, may also be used.

[0126] Preferably, the corrosion inhibitor(s) are distinct from the pH regulating additive(s), in particular making it possible to maintain the pH of the composition between 8 and 15 defined previously.

[0127] An aqueous lubricating composition according to the invention may in particular comprise from 0.1% to 5% by mass of corrosion inhibitor(s), in particular as defined above, preferably from 0.5% to 4% by mass, more preferably from 1% to 2.5% by mass, relative to the total mass of the composition.

[0128] In a particular embodiment, an aqueous lubricating composition according to the invention may comprise at least:

[0129] - water, in particular deionized water; - at least 10% by mass, in particular at least 15% by mass, of one or more polyalkylene glycol(s) with a weight-average molecular mass, Mw, of at least 1500 g / mol;

[0130] - at least one corrosion inhibitor, in particular chosen from corrosion inhibitors organic corrosion, more particularly aliphatic monocarboxylic acids,

[0131] said aqueous lubricating composition comprising a content of additional antifreeze compound(s), in particular chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% by mass, preferably less than or equal to 0.5% by mass, or even less than or equal to 0.1% by mass;

[0132] the contents being expressed relative to the total mass of the composition. Anti-wear / extreme pressure additive

[0133] An aqueous lubricating composition according to the invention may comprise at least one anti-wear and / or extreme pressure additive. Their function is to reduce wear and the coefficient of friction, or to prevent metal-metal contact by forming a protective film adsorbed on these surfaces.

[0134] There is a wide variety of anti-wear additives, among which may be cited those chosen from phosphosulfur additives such as metal alkylthiophosphates or their salts.

[0135] Additives not providing phosphorus may also be suitable, such as, for example, polysulfides, in particular sulfur-containing olefins.

[0136] According to a particular embodiment, an aqueous lubricating composition according to the invention may comprise at least one extreme pressure additive chosen from sulfur-containing fatty acids and dimercaptothiadiazoles, preferably used in their neutralized form, in particular by inorganic alkalizing agents or alkanolamines, emulsifiable or soluble in water.

[0137] Advantageously, an aqueous lubricating composition used according to the invention comprises less than 0.1% by mass of extreme pressure additive of sulfur-containing fatty acid type, in particular in a neutralized form, preferably less than 0.01% by mass, more particularly less than 0.001% by mass, relative to the total mass of the composition, or even is completely free of extreme pressure additive of sulfur-containing fatty acid type.

[0138] The sulfur-containing fatty acids may comprise from 8 to 22 carbon atoms, in particular from 12 to 18 carbon atoms.

[0139] The quantity of sulfur according to standard ASTM D2622 provided by said sulfur-containing fatty acid(s) may be between 5% and 30% by mass, in particular between 10% and 20% by mass, relative to the total mass of the composition.

[0140] Preferably, the quantity of active sulfur at 150°C according to the ASTM D 1662 standard provided by said sulfur-containing fatty acid(s) in the aqueous lubricating composition according to the invention is less than or equal to 2% by mass, in particular less than or equal to 1% by mass, more particularly less than 0.1% by mass, relative to the total mass of the lubricating composition.

[0141] For the purposes of the present invention, the term "active sulfur" means the sulfur that a chemical compound is capable of yielding or releasing when this compound is placed under the conditions of the ASTM DI662 standard. The ASTM D-1662 standard defines an active sulfur level of a compound at a given temperature as a difference expressed as a weight percentage of sulfur content before and after reaction of a sample of this sulfur compound with a given quantity of copper for a fixed time.

[0142] As mentioned above, said sulfur-containing fatty acid(s) are generally used in an aqueous lubricating composition in their form neutralized by an alkalizing agent, such as sodium hydroxide, potassium hydroxide, or an alkanolamine, such as monoethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine and triisopropanolamine.

[0143] An aqueous lubricating composition according to the invention may comprise between 0.01% and 10% by mass of anti-wear and / or extreme pressure additive(s), preferably between 0.2% and 5% by mass, relative to the total mass of the composition. Anti-foam

[0144] An aqueous lubricating composition used according to the invention may comprise at least one anti-foam additive. Anti-foams make it possible to prevent foaming of the lubricating fluid.

[0145] It may be, for example, an anti-foaming agent based on polysiloxanes or acrylate polymers. Preferably, the anti-foaming agent is chosen from three-dimensional siloxanes.

[0146] Also, the antifoaming agents may be polar polymers such as polymethylsiloxanes or polyacrylates.

[0147] In particular, an aqueous lubricating composition according to the invention may comprise from 0.001% to 3.0% by mass of anti-foam additive(s), preferably from 0.005% to 1.5% by mass, more preferably from 0.01% to 1.0% by mass, relative to the total mass of the lubricating composition. Metal passivating agents

[0148] An aqueous lubricating composition according to the invention may comprise at least one metal passivating agent. Metal passivating agents make it possible to protect metal parts by promoting the formation of metal oxide on their surface.

[0149] The metal passivating agents may be chosen, for example, from triazole derivatives, such as tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), amines substituted by a triazole group, such as N,N-bis(2-ethylhexyl)-1,2,4-triazol-1-yl methanamine, N'-bis(2 ethylhexyl)-4-methyl-1H-benzotriazol-1-methyl-amine, N,N-bis(heptyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(nonyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(decyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(undecyl)-ar-methyl-lH-benzotriazole-l-methanamine, N,N-bis(dodecyl)-ar-methyl-lH-benzotriazole-l-methanamine, N,N-bis(2-ethylhexyl)-ar-methyl-lH-benzotriazole-l-methanamine, 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles, 2-alkyldithiobenzothiazoles, 2-(N,N-dialkyldithiocarbamoyl)benzothiazoles, 2,5-bis(alkyldithio)-l,3,4-thiadiazoles, such as 2,5-bis(tert-octyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-nonyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-decyldithio)-l,3,4-thiadiazole, 2,5-bis(tert-undecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-dodecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-tridecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-tetradecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-pentadecyldithio)-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)-l,3,4-thiadiazole, 2,5-bis(N,N-dialkyldithiocarbamoyl)-l,3,4-thiadiazoles, 2-alkyldithio-5-mercaptothiadiazoles, and mixtures thereof.

[0150] Preferably, the metal passivating agents are chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), and their salts, taken alone or in mixtures.

[0151] An aqueous lubricating composition used according to the invention may in particular comprise from 0.01% to 2.0% by mass of metal passivating agent(s), preferably from 0.1% to 1.0% by mass, more preferably from 0.2% to 0.8% by mass, relative to the total mass of the composition.

[0152] In a particular embodiment, an aqueous lubricating composition according to the invention may comprise at least: - water, especially deionized water; - at least 10% by mass, in particular at least 15% by mass, of one or more polyalkylene glycol(s) with a weight-average molecular mass, Mw, of at least 1500 g / mol;

[0153] - at least one metal passivating agent, in particular chosen from derivatives of triazole, more particularly chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), and their salts, taken alone or in mixtures, said aqueous lubricating composition comprising a content of additional antifreeze compound(s), in particular chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% by mass, preferably less than or equal to 0.5% by mass, or even less than or equal to 0.1% by mass; the contents being expressed in relation to the total mass of the composition. Colorants

[0154] An aqueous lubricating composition according to the invention may comprise one or more colorants. The colorants may be natural or synthetic, generally organic.

[0155] The colorants that can be used in an aqueous lubricating composition can be more particularly chosen from natural water-soluble colorants. or synthetic, for example 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 (beetroot), carmine, a chlorophyllin, methylene blue, anthocyanins (enocyanin, black carrot and hibiscus), caramel and riboflavin.

[0156] An aqueous lubricating composition used according to the invention may comprise between 0.01% and 2.0% by mass of colorant(s), preferably between 0.01% and 1.5% by mass, more preferably between 0.02% and 1.0% by mass, relative to the total mass of the composition. Emulsifying agents

[0157] An aqueous lubricating composition used according to the invention may comprise one or more emulsifying agents, also called emulsifiers. Their function is to generate stable emulsions in water.

[0158] The emulsifying agents may be more particularly non-ionic, such as for example ethoxylated fatty alcohols, ethoxylated fatty acids, ethoxylated fatty amides; anionic, for example KOH, NaOH soaps; sulfonates; cationic, such as quaternary ammonium compounds; or even carboxylic acid esters which are soluble or emulsifiable in water.

[0159] In particular, an aqueous lubricating composition according to the invention may comprise from 0.01% to 10% by mass of emulsifying agent(s), preferably from 0.1% to 5.0% by mass, relative to the total mass of the lubricating composition. Sequestering agents

[0160] An aqueous lubricating composition used according to the invention may comprise at least one sequestering agent. Sequestering agents, also called chelating agents, make it possible to limit the incrustation of metal ions in the composition.

[0161] Examples of sequestering agents include those derived from phosphonic acids and phosphonates, such as diethylenetriaminepentamethylphosphonic acid (DTPMPA), aminotri(methylenephosphonic acid) (ATMP), hydroxyethanediphosphonic acid (HEDP), 1-hydroxyethylidene 1,1-diphosphonate, 2-hydroxyethylaminedi(methylenephosphonic acid) (HEAMBP), diethylenetriaminopenta(methylenephosphonic acid) (DTMP), multifunctional 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 rinulin, carboxymethylinulin and carboxymethylchitosan.

[0162] An aqueous lubricating composition according to the invention may comprise from 0.001% to 2.0% by mass of sequestering agent(s), preferably from 0.01% to 1.0% by mass, relative to the total mass of the composition. Biocides and fungicides

[0163] An aqueous lubricating composition according to the invention may comprise at least one biocidal and / or fungicidal agent. The biocides and fungicides may be used to improve the biological stability of the composition by limiting the proliferation of bacteria, fungi and yeasts in the lubricating fluid.

[0164] Such biocides may be chosen from parabens, aldehydes, reactive acetylacetone compounds, isothiazolinones, phenolic compounds, acid salts, halogenated compounds, quaternary ammoniums, certain alcohols and mixtures thereof.

[0165] Preferably, the biocides may be chosen from optionally substituted benzisothiazolinones (BIT), such as N-butyl-1,2-benzisothiazolin-3-one, methylisothiazolinones (MIT), mixtures of methylisothiazolinone and chloromethylisothiazolinone (MIT / CMIT), orthophenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate (IPBC), chlorocresol and N,N-methylene-bis-morpholine (MBM); sorbic acid; preferably from orthophenyl-phenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate, chloro-cresol, benzisothiazolinones and N,N-methylene-isomorpholine.

[0166] An aqueous lubricating composition according to the invention may in particular comprise between 0.01% and 10% by mass of biocide(s) and / or fungicide(s), preferably between 0.5% and 5.0% by mass, relative to the total mass of the composition.

[0167] It is understood that the various particular embodiments described above may be combined, to the extent possible, to define other particular embodiments.

[0168] In particular, each of the additives specifically described above can be introduced alone, or in combination with at least one other of the additives specifically described, which defines different variant embodiments of an aqueous lubricating composition according to the invention.

[0169] In a particular embodiment, an aqueous lubricating composition according to the invention comprises at least: - water, especially deionized water; - at least 10% by mass, in particular at least 15% by mass, of one or more polyalkylene glycol(s) with a weight-average molecular mass, Mw, of at least 1500 g / mol;

[0170] - one or more additives chosen from anti-foaming agents, inhibitors of corrosion, pH regulators, metal passivating agents, dyes, in particular as defined above, said aqueous lubricating composition comprising a content of additional antifreeze compound(s), in particular chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% by mass, preferably less than or equal to 0.5% by mass, or even less than or equal to 0.1% by mass;

[0171] the contents being expressed relative to the total mass of said composition.

[0172] In a particular embodiment, an aqueous lubricating composition according to the invention comprises at least: - at least 15% by mass of water, in particular demineralized water, for example deionized water, preferably at least 30% by mass, more particularly from 30% to 85% by mass; - at least 10% by mass, in particular at least 15% by mass, in particular from 15% to 50% by mass, more particularly from 15% to 30% by mass, of one or more polyalkylene glycol(s) with a weight-average molecular mass, Mw, of at least 1500 g / mol;

[0173] - from 0.1 to 10% by mass, in particular from 1.0 to 5.0% by mass, of one or more additives chosen from anti-foaming agents, corrosion inhibitors, pH regulators, metal passivating agents, colorants, in particular as defined above, said aqueous lubricating composition comprising a content of additional antifreeze compound(s), in particular chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% by mass, preferably less than or equal to 0.5% by mass, or even less than or equal to 0.1% by mass;

[0174] the contents being expressed relative to the total mass of said composition.

[0175] In particular, an aqueous lubricating composition according to the invention may consist of:

[0176] - at least 10% by mass, in particular at least 15% by mass, in particular of 15% to 50% by mass, more particularly 15% to 30% by mass, of one or more polyalkylene glycol(s) with a weight-average molecular mass, Mw, of at least 1500 g / mol;

[0177] - from 0.1 to 10% by mass, in particular from 1.0 to 5.0% by mass, of one or more additives chosen from anti-foaming agents, corrosion inhibitors, pH regulators, metal passivating agents, colorants, in particular as defined above, said aqueous lubricating composition comprising a content of additional antifreeze compound(s), in particular chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% mass, preferably less than or equal to 0.5% by mass, or even less than or equal to 0.1% by mass;

[0178] the contents being expressed relative to the total mass of the composition; the remainder being made up of water, preferably deionized water.

[0179] A lubricating composition according to the invention advantageously has a kinematic viscosity, measured at 40°C according to standard ASTM D445, of between 20 mm2 / s and 1000 mm2 / s, preferably between 25 mm2 / s and 100 mm2 / s.

[0180] Advantageously, a lubricating composition according to the invention has a viscosity index of between 100 and 300, preferably of between 150 and 350.

[0181] As mentioned previously, a lubricating composition according to the invention exhibits good performance in terms of cold properties.

[0182] The low temperature Brookfield viscosity of a lubricating composition quantifies its ability to remain liquid at very low temperatures and in particular is representative of its ability to retain its properties when cold.

[0183] In particular, a lubricating composition according to the invention may have a Brookfield viscosity, measured at -40°C according to the ASTM D2983 standard, of between 1000 mPa.s and 100,000 mPa.s, preferably between 5,000 mPa.s and 60,000 mPa.s. APPLICATION

[0184] Aqueous lubricating compositions can find various applications. Generally, they can be used as lubricating fluid for systems and applications, as a substitute for conventional hydrocarbon lubricants.

[0185] The invention is thus not limited to a particular application of the aqueous lubricants according to the invention, the following development being given solely for illustrative and non-limiting purposes.

[0186] The mechanical parts lubricated using a lubricating composition according to the invention can be made of any material conventionally used in the fields concerned, in particular metal, such as steel, galvanized steel, stainless steel, yellow metals, but also ceramic or polymer material.

[0187] It is understood that the surface of these different materials can be coated, for example with a DLC coating (for “Diamond Like Carbon” in English).

[0188] As an illustration of a possible application, an aqueous lubricating composition according to the invention may be intended to lubricate moving parts in a mechanical system, and more particularly intended to lubricate a mobile or stationary motorization system.

[0189] An aqueous lubricating composition according to the invention can thus be used for the lubrication and / or cooling of gears, rolling bearings, bearings, such as rolling or sliding bearings or even motors.

[0190] For the purposes of the present invention, the term "motorization system" is intended to denote a system comprising all the mechanical parts necessary for the intended mobile or stationary application and including at least one engine. It may be a combustion, gas, electric or hybrid motorization system, depending on the nature of the engine(s) included in the motorization system: combustion, gas, and / or electric engine.

[0191] A “stationary” motorization system within the meaning of the invention is a motorization system including a stationary engine. It may find applications, for example, in devices for producing electrical energy. It may in particular be a gas motorization system, in particular a stationary gas engine.

[0192] A “mobile” motorization system is more particularly a motorization system implemented in vehicles, including light vehicles, heavy goods vehicles, so-called “off-road” mobile machines, or even marine vehicles.

[0193] A mobile motorization system can thus be a propulsion system for a vehicle, in particular a combustion vehicle, an electric vehicle or even a hybrid vehicle.

[0194] For the purposes of the present invention, the term "propulsion system" is understood to mean a system comprising the mechanical parts necessary for the propulsion of a vehicle. The propulsion system more particularly encompasses a motor, for example an electric motor comprising the rotor-stator assembly of the power electronics (dedicated to speed regulation), a transmission and possibly a battery. The battery itself is generally made up of a set of electrical accumulators, called cells.

[0195] An aqueous lubricating composition according to the invention advantageously makes it possible to act effectively on fuel consumption via its impact on the friction forces generated between the various components of motor vehicles. In particular, an aqueous lubricating composition proves to be particularly advantageous for reducing friction in gearboxes, in axle differentials and / or in the cylinder head.

[0196] By thus reducing friction between moving parts in the vehicle's propulsion system, a lubricating composition according to the invention not only reduces wear, but also limits energy losses responsible for excess fuel consumption.

[0197] An aqueous lubricating composition according to the invention thus advantageously has good properties in terms of reducing the fuel consumption of motor vehicles, also known as “Fuel Eco” properties and, in fact, contributes to the reduction of CO2 emissions.

[0198] An aqueous lubricating composition according to the invention may find an interesting application for the lubrication and / or cooling of an electric or hybrid vehicle propulsion system, and more particularly of the engine, the power electronics, the transmission and / or the battery.

[0199] An aqueous composition according to the invention can be used both as a cooling fluid and as a lubricant, for example in a propulsion system of an electric or hybrid vehicle. Advantageously, a composition according to the invention makes it possible to jointly achieve good properties in terms of cooling and lubrication of the parts of the propulsion system of an electric or hybrid vehicle, such as an electric motor of an electric or hybrid vehicle. It proves to be particularly effective for cooling the power electronics and / or the rotor and / or the stator of an electric motor. It also ensures the lubrication of the bearings located between the rotor and the stator of an electric motor of an electric or hybrid vehicle.

[0200] Also, a composition according to the invention advantageously makes it possible to effectively cool the battery present in an electric or hybrid vehicle.

[0201] Thus, advantageously, it is for example possible, by implementing a single composition according to the invention, to ensure both the cooling of the battery and the lubrication of the transmission, in particular the reducer, in an electric or hybrid vehicle.

[0202] An aqueous lubricating composition according to the invention can be used as a running-in lubricant, for example for running-in mobile or stationary motorization systems.

[0203] Indeed, new or refurbished mechanical systems may require, during the first start-ups, appropriate lubrication in order to avoid initial damage to the surface of the parts until the mechanical system reaches its optimal operation.

[0204] As mentioned above, an aqueous lubricating composition according to the invention may also find applications as a hydraulic fluid, in particular in hydraulic actuators (cylinders / motors) or machine assemblies on demand. In particular, hydraulic fluids are subjected to constant mechanical stresses and high shear due to their constant passage through a pump in order to maintain an appropriate pressure in the hydraulic system.

[0205] Thus, an aqueous lubricating composition according to the invention can be used for the lubrication of the various moving parts in a hydraulic system. It can also ensure heat transfer between the various components of a hydraulic system.

[0206] All of the applications detailed above make it possible to illustrate certain advantageous implementations of an aqueous lubricating composition according to the invention.

[0207] According to the invention, the particular, advantageous or preferred characteristics defined for a composition according to the invention make it possible to define uses according to the invention which are also particular, advantageous or preferred.

[0208] The invention will now be described by means of the following examples given of course by way of illustration and not limitation of the invention. Example 1

[0209] Preparation of aqueous solutions of polyalkylene glycol

[0210] The polyalkylene glycol used in this example is a random copolymer of ethylene oxide (EO) / propylene oxide (PO) with a molecular mass of 21,000 g / mol, having an EO / PO mass ratio of 80 / 20, formed from a polyol-type initiator, pentaerythritol, and comprising hydroxyl endings.

[0211] Four solutions S1, S2, S3 and S4 are prepared by simple mixing, at room temperature, polyalkylene glycol with deionized water in increasing proportions (20% to 80%), as indicated in the following table 1. The percentages are expressed by mass relative to the total mass of the composition.

[0212] Their pour point is measured according to ISO 3016.

[0213] The pour point of deionized water alone C0 and polyalkylene glycol alone C5 is also measured.

[0214] The values ​​of the flow point measurements are reported in Table 1 below.

[0215] [Tables 1] CO SI S2 S3 S4 C5 Deionized water [%] 100 80 60 35 20 0 Pdialkylene glycol [%] 0 20 40 65 80 100 Pour point | C j 0 -15 -21 -30 -21 0

[0216] It is observed that the mixture of deionized water and polyalkylene glycol makes it possible to lower the pour point, compared to pure water. These tests therefore demonstrate the antifreeze properties of polyalkylene glycol used in water. Example 2 Preparation of lubricating compositions

[0217] The polyalkylene glycols considered in this example are:

[0218] - PAG 1: non-biosourced, commercially available polyalkylene glycol, which is a random EO / OP copolymer with a molecular mass of 14300 g / mol having two terminal hydroxyl groups, and a kinematic viscosity at 40°C of 55,000 mm2 / s;

[0219] - PAG 2: bio-sourced polyalkylene glycol, chemically similar to PAG 1 (OE / OP copolymer with terminal hydroxyl functions), also commercially available, with a molecular weight of 26000 g / mol and a kinematic viscosity at 50°C of 40,000 mm2 / s.

[0220] Aqueous lubricants (CL1 and CL2) according to the invention, using PAG 1 and PAG 2, are formulated according to the composition indicated in the following table and compared to a commercialized aqueous lubricant CCI using a glycol (diethylene glycol) as antifreeze.

[0221] The percentages are expressed in mass relative to the total mass of the composition.

[0222] [Tables2] | CCI CL1 CL2 Deionized water [%] ri xJ- 80.60 80.60 PAG 1 [%] 14.25 16.00 - PAG 2 [%] । ' - 16.00 Diethylene glycol [%] 40.00 - - Additive package 1^ [%] 3.1 Additive package 2f':i [%] 3.4 3.4 'Additive packages 1 and 2 are additive blends comprising one or more pH regulating additives, one or more anti-corrosion additives, one or more metal passivating agents, one or more anti-foam additives and / or one or more colorants. The environmental footprint of additive package 2 is similar to or even slightly higher than additive package I. Environmental footprint

[0223] The environmental footprint associated with the production of each of the lubricants is assessed according to different indicators defined by the European Union, and based on data communicated by the manufacturers.

[0224] Climate change indicator

[0225] The so-called "climate change" indicator is estimated for the three aforementioned lubricants. This indicator refers to the increase in average temperatures as a result of greenhouse gas emissions. The global warming potential of all greenhouse gas emissions is measured in kilogram carbon dioxide equivalent (kg CO2 eq), i.e. all greenhouse gases are compared to the amount of warming potential of 1 kg of CO2.

[0226] The results of the assessment of this indicator, expressed as a percentage for CL1 and CL2 lubricants compared to the CCI reference lubricant (100%), are presented in [Fig.l].

[0227] They highlight a significant reduction in the impact on climate change of the CL1 formulation according to the invention and even more so of the CL2 formulation incorporating a bio-sourced PAG, compared to the commercial CCI lubricant using diethylene glycol as an antifreeze additive.

[0228] The following other indicators are estimated for CL1 and CCI lubricants.

[0229] Ozone layer impact indicator: The potential impacts of all substances that can lead to ozone depletion are converted to their equivalent in kilograms of trichlorofluoromethane, the unit of measurement is therefore kilograms of CFC-11 equivalent (kg CFC-11 eq).

[0230] Photochemical ozone formation: The potential impact of substances contributing to photochemical ozone formation is converted to kilogram equivalents of non-methane volatile organic compounds (e.g., alcohols, aromatics, etc.; kg NMVOC eq).

[0231] Particulate matter emissions: This indicator measures the negative impacts on human health caused by emissions of particulate matter (PM) and its precursors (e.g. NOX, SO2). The potential impact is measured as the change in mortality due to particulate matter emissions, expressed as incidence of disease per kg of PM2 5 (particles with diameters of 2.5 pm) emitted.

[0232] Human toxicity: This indicator refers to the potential impacts on human health caused by substances absorbed through air, water and soil. The unit of measurement is the “Comparative Toxic Unit for Humans” (CTUh). This is based on a model called USEtox.

[0233] Acidification: Acidification can be caused by emissions that enter the air, water, and soil. The most important sources are combustion processes in electricity production, heating, and transportation. The potential impact of substances contributing to acidification is converted to mole equivalents of hydron (eq mol H+).

[0234] Eutrophication, freshwater: Eutrophication impacts ecosystems due to substances containing nitrogen (N) or phosphorus (P). The potential impact of substances contributing to freshwater eutrophication is converted into kilograms of phosphorus equivalent (kg P eq).

[0235] Ecotoxicity, freshwater: This indicator refers to the potential toxic impacts on an ecosystem. The unit of measurement is the comparative toxic unit for ecosystems (CTUe). This is based on a model called USEtox.

[0236] Water consumption: The potential impact is expressed in cubic meters (m3) of water use.

[0237] Use of fossil resources: The amount of materials contributing to the use of fossil resources is converted into MJ.

[0238] The results of the assessment of these different indicators, expressed as a percentage for the CL1 lubricant compared to the CCI reference lubricant (100%), are presented in [Fig.l].

[0239] Generally speaking, the aqueous lubricants formulated according to the invention allow a reduction in the environmental impact assessed via the various aforementioned criteria.

Claims

Claims

1. Use of at least one polyalkylene glycol, denoted PAG, with a weight-average molecular mass, Mw, of at least 1500 g / mol, as an antifreeze agent in an aqueous lubricating composition.

2. Use according to the preceding claim, said polyalkylene glycol(s) being used in an amount of at least 10% by mass, in particular from 15% to 50% by mass, more particularly from 15% to 30% by mass, relative to the total mass of the aqueous lubricating composition.

3. Use according to claim 1 or 2, said aqueous lubricating composition comprising at least 15% by mass of water, in particular demineralized water, for example deionized water, preferably at least 30% by mass, more particularly from 30% to 85% by mass.

4. Use according to any one of the preceding claims, wherein said polyalkylene glycol 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.

5. Use according to any one of the preceding claims, in which said polyalkylene glycol is a copolymer, in particular a random copolymer, of ethylene oxide (EO) and propylene oxide (PO), preferably comprising the ethylene oxide (EO) and propylene oxide (PO) units in an EO / PO mass ratio of between 50 / 50 and 90 / 10, in particular between 60 / 40 and 85 / 15, and more particularly between 70 / 30 and 80 / 20.

6. Use according to any one of the preceding claims, wherein said polyalkylene glycol comprises hydroxyl terminal functions.

7. Use according to any one of the preceding claims, wherein said polyalkylene glycol has a cloud point determined according to ASTM D 2024, in particular greater than or equal to 70°C.

8. Use according to any one of the preceding claims, wherein said polyalkylene glycol has a kinematic viscosity measured at 100°C (KV100), according to ASTM D445, of between 100 and 25,000 mm2 / s, in particular between 150 and 15,000 mm2 / s.

9. Use according to any one of the preceding claims, wherein said polyalkylene glycol has a kinematic viscosity measured at 40°C (KV40), according to ASTM D445, between 500 and 100,000 mm2 / s, more particularly between 1,000 and 70,000 mm2 / s.

10. Use according to any one of the preceding claims, wherein said polyalkylene glycol has a flash point measured by ISO 2592 greater than or equal to 160°C, in particular greater than or equal to 220°C.

11. Use according to any one of the preceding claims, the polyalkylene glycol(s) having a weight-average molecular mass of at least 2000 g.mol *, in particular at least 2500 g.mol *, more particularly at least 3000 g.mol *, in particular between 3000 and 50,000 g.mol *, or even between 5,000 and 25,000 g.mol *.

12. Use according to any one of the preceding claims, wherein said polyalkylene glycol is bio-sourced.

13. Use according to any one of the preceding claims, said aqueous lubricating composition comprising a content of additional antifreeze compound(s), in particular chosen from glycols, in particular alkylene glycols having from 2 to 6 carbon atoms such as monoethylene glycol and / or monopropylene glycol and oxyalkylene glycols having from 4 to 14 carbon atoms such as diethylene glycol; aliphatic monoethers of said glycols and polyhydric aliphatic alcohols such as glycerol, strictly less than 5% by mass, in particular strictly less than 1% by mass, and more particularly less than or equal to 0.1% by mass, relative to the total mass of said aqueous lubricating composition.

14. Use according to any one of the preceding claims, for improving the climate change indicator of said aqueous lubricating composition.

15. Aqueous lubricating composition comprising at least: - water, in particular deionized water; - at least 10% by mass, relative to the total mass of said composition, of one or more polyalkylene glycol(s) with a weight-average molecular mass, Mw, of at least 1500 g.mol *, said aqueous lubricating composition comprising a content strictly less than 1% by mass, relative to the total mass of said composition, of additional antifreeze compound(s), in particular chosen from glycols, in particular alkylene glycols having from 2 to 6 carbon atoms such as monoethylene glycol and / or mono- propylene glycol and oxyalkylene glycols having from 4 to 14 carbon atoms such as diethylene glycol; aliphatic monoethers of said glycols and polyhydric aliphatic alcohols such as glycerol.

16. Aqueous lubricating composition according to the preceding claim comprising at least 15% by mass, in particular from 15% to 50% by mass, more particularly from 15% to 30% by mass, or even from 16% to 20% by mass, of said polyalkylene glycol(s), relative to the total mass of the aqueous lubricating composition.

17. Aqueous lubricating composition according to claim 15 or 16, in which the PAG(s) / water mass ratio is less than or equal to 0.30, in particular between 0.10 and 0.30, more particularly between 0.15 and 0.25, and in particular between 0.15 and 0.

20.

18. An aqueous lubricating composition according to any one of claims 15 to 17, wherein said polyalkylene glycol(s) are as defined in any one of claims 4 to 12.

19. An aqueous lubricating composition according to any one of claims 15 to 18, further comprising at least one additive selected from antifoaming agents, biocides, pH regulators, corrosion inhibitors, antiwear and / or extreme pressure additives, sequestering agents, metal passivating agents, colorants, dispersants, emulsifying agents, and mixtures thereof, preferably selected from antifoaming agents, extreme pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, colorants, and mixtures thereof.

20. Use of an aqueous lubricating composition as defined in any one of claims 15 to 19 for the lubrication and / or cooling of moving parts in a mechanical system, for example for the lubrication and / or cooling of mobile or stationary motorization systems, or as a hydraulic fluid.

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